Problem water pump Yanmar 2GM
 

Hello all,

I recently did a standard maintenance replacement of a raw water impeller
on a Yanmar 2GM diesel. Everything seemed straightfoward, part for part,
no leakage, everything went back together straight away and test runs at
the dock were nominal.

However, during a move to a new slip the engine alarm went off. A
subsequent check revealed nothing. Took the boat out and ran the engine
for a good hour and there were no issues. The second time out the engine
alarm went off again after about the same duration of running time as the
incident during the move to the new slip.

This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

The boat is a 1989 S2.

I am stumped. Any suggestions would be infinitely appreciated.

Thanks,

Problem water pump Yanmar 2GM
 

"Jeffrey P. Vasquez" wrote in
message ...

This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

Egress from downstream of the pump? or to the pump inlet?

Now I don't know the details of your Yanmar, but here goes -

Where is your over-temperature sensor? In the fresh water system? Salt water
system or in the exhaust? That'll tell you quite a bit and may answer later
questions.

So, just to confirm, is salt water flowing from the exhaust/outlet when the
engine is running?

If in normal quantity, then there's likely to be a fresh water flow problem
(if the overheat sensor is in the fresh water system).

If reduced quantity, then there's likely to be a partial salt water blockage
which may not show up in a simple check, but which will effect cooling at
higher revs.

If no water, there's either a blockage which you haven't detected
(downstream of pump?) or the pump is not pumping.

You can check most pumps by taking the cover off and turning the engine over
with the starter while holding the fuel cut-off. If the vanes don't turn,
there's a shear failure somewhere or a missing key, and that's your problem.
If they do turn - your pump is almost certainly OK. Back to the partial
blockage . . .

Have fun. Maybe someone who knows your Yanmar will give you a better story.
--
JimB
Yacht Rapaz, sadly for sale:
http://homepage.ntlworld.com/jim.bae...cification.htm
jim(dot)baerselman(at)ntlworld(dot)com

Problem water pump Yanmar 2GM
 

"Jeffrey P. Vasquez" wrote in
message ...

This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

Egress from downstream of the pump? or to the pump inlet?

Now I don't know the details of your Yanmar, but here goes -

Where is your over-temperature sensor? In the fresh water system? Salt water
system or in the exhaust? That'll tell you quite a bit and may answer later
questions.

So, just to confirm, is salt water flowing from the exhaust/outlet when the
engine is running?

If in normal quantity, then there's likely to be a fresh water flow problem
(if the overheat sensor is in the fresh water system).

If reduced quantity, then there's likely to be a partial salt water blockage
which may not show up in a simple check, but which will effect cooling at
higher revs.

If no water, there's either a blockage which you haven't detected
(downstream of pump?) or the pump is not pumping.

You can check most pumps by taking the cover off and turning the engine over
with the starter while holding the fuel cut-off. If the vanes don't turn,
there's a shear failure somewhere or a missing key, and that's your problem.
If they do turn - your pump is almost certainly OK. Back to the partial
blockage . . .

Have fun. Maybe someone who knows your Yanmar will give you a better story.
--
JimB
Yacht Rapaz, sadly for sale:
http://homepage.ntlworld.com/jim.bae...cification.htm
jim(dot)baerselman(at)ntlworld(dot)com

Problem water pump Yanmar 2GM
 

On Sun, 04 Jan 2004 09:35:34 GMT, "Jeffrey P. Vasquez"
wrote this crap:

Hello all,

I recently did a standard maintenance replacement of a raw water impeller
on a Yanmar 2GM diesel. Everything seemed straightfoward, part for part,
no leakage, everything went back together straight away and test runs at
the dock were nominal.

However, during a move to a new slip the engine alarm went off. A
subsequent check revealed nothing. Took the boat out and ran the engine
for a good hour and there were no issues. The second time out the engine
alarm went off again after about the same duration of running time as the
incident during the move to the new slip.


This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

Was there water coming out the water exit while the motor was running?




This signature is now the ultimate power in the universe

Problem water pump Yanmar 2GM
 

On Sun, 04 Jan 2004 09:35:34 GMT, "Jeffrey P. Vasquez"
wrote this crap:

Hello all,

I recently did a standard maintenance replacement of a raw water impeller
on a Yanmar 2GM diesel. Everything seemed straightfoward, part for part,
no leakage, everything went back together straight away and test runs at
the dock were nominal.

However, during a move to a new slip the engine alarm went off. A
subsequent check revealed nothing. Took the boat out and ran the engine
for a good hour and there were no issues. The second time out the engine
alarm went off again after about the same duration of running time as the
incident during the move to the new slip.


This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

Was there water coming out the water exit while the motor was running?




This signature is now the ultimate power in the universe

Problem water pump Yanmar 2GM
 

While it has never happened to me I have heard the hoses to the pump can
delaminate. They will look normal on the outside but the inner rubber has
separated from the outer and is drawn in by the flow. When drawn in it
restricts the flow and causes a vacuum which causes more hose to plug.
Sometimes the entire hose is sucked it which is a dead give away.

"Horvath" wrote in message
...
On Sun, 04 Jan 2004 09:35:34 GMT, "Jeffrey P. Vasquez"
wrote this crap:

Hello all,

I recently did a standard maintenance replacement of a raw water impeller
on a Yanmar 2GM diesel. Everything seemed straightfoward, part for part,
no leakage, everything went back together straight away and test runs at
the dock were nominal.

However, during a move to a new slip the engine alarm went off. A
subsequent check revealed nothing. Took the boat out and ran the engine
for a good hour and there were no issues. The second time out the engine
alarm went off again after about the same duration of running time as the
incident during the move to the new slip.


This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

Was there water coming out the water exit while the motor was running?




This signature is now the ultimate power in the universe

Problem water pump Yanmar 2GM
 

While it has never happened to me I have heard the hoses to the pump can
delaminate. They will look normal on the outside but the inner rubber has
separated from the outer and is drawn in by the flow. When drawn in it
restricts the flow and causes a vacuum which causes more hose to plug.
Sometimes the entire hose is sucked it which is a dead give away.

"Horvath" wrote in message
...
On Sun, 04 Jan 2004 09:35:34 GMT, "Jeffrey P. Vasquez"
wrote this crap:

Hello all,

I recently did a standard maintenance replacement of a raw water impeller
on a Yanmar 2GM diesel. Everything seemed straightfoward, part for part,
no leakage, everything went back together straight away and test runs at
the dock were nominal.

However, during a move to a new slip the engine alarm went off. A
subsequent check revealed nothing. Took the boat out and ran the engine
for a good hour and there were no issues. The second time out the engine
alarm went off again after about the same duration of running time as the
incident during the move to the new slip.


This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

Was there water coming out the water exit while the motor was running?




This signature is now the ultimate power in the universe

Problem water pump Yanmar 2GM
 

"Jeffrey P. Vasquez" wrote in


This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

"JimB" wrote in message news:...

snip
You can check most pumps by taking the cover off and turning the engine over
with the starter while holding the fuel cut-off. If the vanes don't turn,
there's a shear failure somewhere or a missing key, and that's your problem.
If they do turn - your pump is almost certainly OK. Back to the partial
blockage . . .

Have fun. Maybe someone who knows your Yanmar will give you a better story.

I had a VERY frustrating overheating problem, sounds VERY similar to
what Jeff describes and Jim has Almost focused on what the problem
was . For me it was very frustrating, check strainer, check hoses,
check impeller, (still overheats) check pump (ok), pull exhaust
(still overheats), replace w new impeller (still overheats) put in 2nd
new impeller (still overheats) damn thing would run FINE at idle in
the canal, when I get out the channel and pick up rpm it would
overheat., seastrainer clear from beginning, no air leaks.

take pump cover off, R&R impeller & never find anything wrong. Put it
back together and runs fine at idle. (sound familiar Jeff?)

Finally I discovered what was happening was what Jim alluded to -- a
shear failure. Where the pulley fits on the water pump shaft was the
problem. There was enough drag to (pump off engine) to turn the pulley
by hand and observe the shaft spin & impeller turn (offering NO CLUE
because it APPEARED to be OK). Under load the drag was overcome and
EVEN THOUGH I could see the belt spinning the pulley, the drag on the
impeller overcame the shaft/pulley drag .

The problem was Both the pulley and the shaft, couldn't just relace
the pulley had to replace the shaft, to replace the shaft needed new
bearings and seals & by the time you add the shaft, bearings, seals, &
pulley together as a parts order it made more sense (cents!) to just
buy a new pump assembly (not cheap either)

Problem water pump Yanmar 2GM
 

"Jeffrey P. Vasquez" wrote in


This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

"JimB" wrote in message news:...

snip
You can check most pumps by taking the cover off and turning the engine over
with the starter while holding the fuel cut-off. If the vanes don't turn,
there's a shear failure somewhere or a missing key, and that's your problem.
If they do turn - your pump is almost certainly OK. Back to the partial
blockage . . .

Have fun. Maybe someone who knows your Yanmar will give you a better story.

I had a VERY frustrating overheating problem, sounds VERY similar to
what Jeff describes and Jim has Almost focused on what the problem
was . For me it was very frustrating, check strainer, check hoses,
check impeller, (still overheats) check pump (ok), pull exhaust
(still overheats), replace w new impeller (still overheats) put in 2nd
new impeller (still overheats) damn thing would run FINE at idle in
the canal, when I get out the channel and pick up rpm it would
overheat., seastrainer clear from beginning, no air leaks.

take pump cover off, R&R impeller & never find anything wrong. Put it
back together and runs fine at idle. (sound familiar Jeff?)

Finally I discovered what was happening was what Jim alluded to -- a
shear failure. Where the pulley fits on the water pump shaft was the
problem. There was enough drag to (pump off engine) to turn the pulley
by hand and observe the shaft spin & impeller turn (offering NO CLUE
because it APPEARED to be OK). Under load the drag was overcome and
EVEN THOUGH I could see the belt spinning the pulley, the drag on the
impeller overcame the shaft/pulley drag .

The problem was Both the pulley and the shaft, couldn't just relace
the pulley had to replace the shaft, to replace the shaft needed new
bearings and seals & by the time you add the shaft, bearings, seals, &
pulley together as a parts order it made more sense (cents!) to just
buy a new pump assembly (not cheap either)

Problem water pump Yanmar 2GM
 

"JimB" wrote in message ...
"Jeffrey P. Vasquez" wrote in
message ...

This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

Egress from downstream of the pump? or to the pump inlet?

Now I don't know the details of your Yanmar, but here goes -

Where is your over-temperature sensor? In the fresh water system? Salt water
system or in the exhaust? That'll tell you quite a bit and may answer later
questions.

So, just to confirm, is salt water flowing from the exhaust/outlet when the
engine is running?

If in normal quantity, then there's likely to be a fresh water flow problem
(if the overheat sensor is in the fresh water system).

If reduced quantity, then there's likely to be a partial salt water blockage
which may not show up in a simple check, but which will effect cooling at
higher revs.

If no water, there's either a blockage which you haven't detected
(downstream of pump?) or the pump is not pumping.

You can check most pumps by taking the cover off and turning the engine over
with the starter while holding the fuel cut-off. If the vanes don't turn,
there's a shear failure somewhere or a missing key, and that's your problem.
If they do turn - your pump is almost certainly OK. Back to the partial
blockage . . .

Have fun. Maybe someone who knows your Yanmar will give you a better story.

Had nearly the same problem on a used 2GM I installed on my 28' S2.
The problem was downstream of the water pump at the outlet of the
cooling jacket. Salt and corrosion had built up to stop the flow. It
took some time to remove the corrosion and salt but it now flows fine.
It has been a couple of weeks since I looked at the engine so I do
not recall the layout.

David OHara
"Ragtime"

Problem water pump Yanmar 2GM
 

"JimB" wrote in message ...
"Jeffrey P. Vasquez" wrote in
message ...

This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

Egress from downstream of the pump? or to the pump inlet?

Now I don't know the details of your Yanmar, but here goes -

Where is your over-temperature sensor? In the fresh water system? Salt water
system or in the exhaust? That'll tell you quite a bit and may answer later
questions.

So, just to confirm, is salt water flowing from the exhaust/outlet when the
engine is running?

If in normal quantity, then there's likely to be a fresh water flow problem
(if the overheat sensor is in the fresh water system).

If reduced quantity, then there's likely to be a partial salt water blockage
which may not show up in a simple check, but which will effect cooling at
higher revs.

If no water, there's either a blockage which you haven't detected
(downstream of pump?) or the pump is not pumping.

You can check most pumps by taking the cover off and turning the engine over
with the starter while holding the fuel cut-off. If the vanes don't turn,
there's a shear failure somewhere or a missing key, and that's your problem.
If they do turn - your pump is almost certainly OK. Back to the partial
blockage . . .

Have fun. Maybe someone who knows your Yanmar will give you a better story.

Had nearly the same problem on a used 2GM I installed on my 28' S2.
The problem was downstream of the water pump at the outlet of the
cooling jacket. Salt and corrosion had built up to stop the flow. It
took some time to remove the corrosion and salt but it now flows fine.
It has been a couple of weeks since I looked at the engine so I do
not recall the layout.

David OHara
"Ragtime"

Problem water pump Yanmar 2GM
 

"JimB" wrote in message ...
"Jeffrey P. Vasquez" wrote in
message new

You can check most pumps by taking the cover off and turning the engine over
with the starter while holding the fuel cut-off. If the vanes don't turn,
there's a shear failure somewhere or a missing key, and that's your problem.
If they do turn - your pump is almost certainly OK. Back to the partial
blockage . . .

jUST adding a little, Did you replace the wear plate on your pump? Is
it a jabsco? If it is a jabsco and you did not replace the wear plate
that might be a good place to start. Are you getting the same amount
of water out of your exhaust? If so than its you fresh water pump, or
like jeffery said perhaps your heat exchanger is clogged up.


Good luck

Joe

Have fun. Maybe someone who knows your Yanmar will give you a better story.

Problem water pump Yanmar 2GM
 

"JimB" wrote in message ...
"Jeffrey P. Vasquez" wrote in
message new

You can check most pumps by taking the cover off and turning the engine over
with the starter while holding the fuel cut-off. If the vanes don't turn,
there's a shear failure somewhere or a missing key, and that's your problem.
If they do turn - your pump is almost certainly OK. Back to the partial
blockage . . .

jUST adding a little, Did you replace the wear plate on your pump? Is
it a jabsco? If it is a jabsco and you did not replace the wear plate
that might be a good place to start. Are you getting the same amount
of water out of your exhaust? If so than its you fresh water pump, or
like jeffery said perhaps your heat exchanger is clogged up.


Good luck

Joe

Have fun. Maybe someone who knows your Yanmar will give you a better story.

Problem water pump Yanmar 2GM
 

In article ,
"Jeffrey P. Vasquez"
wrote:

I recently did a standard maintenance replacement of a raw water impeller
on a Yanmar 2GM diesel. Everything seemed straightfoward, part for part,
no leakage, everything went back together straight away and test runs at
the dock were nominal.

However, during a move to a new slip the engine alarm went off. A
subsequent check revealed nothing.

Try the impeller you took out -- it sounds like it was working before.
Happened to us once. We got just enough flow for idle power.

After that, I'd dismount the pump, leaving the input hose on, put the
output into a bucket and power it with a drill. If you get good output,
then it's downstream.

We also found out that we have about 5 minutes' cruise power with no raw
water flow: Takes that long for the fresh water loop to get hot.
Probably takes longer if you have a domestic hot water tank in the loop.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

Problem water pump Yanmar 2GM
 

In article ,
"Jeffrey P. Vasquez"
wrote:

I recently did a standard maintenance replacement of a raw water impeller
on a Yanmar 2GM diesel. Everything seemed straightfoward, part for part,
no leakage, everything went back together straight away and test runs at
the dock were nominal.

However, during a move to a new slip the engine alarm went off. A
subsequent check revealed nothing.

Try the impeller you took out -- it sounds like it was working before.
Happened to us once. We got just enough flow for idle power.

After that, I'd dismount the pump, leaving the input hose on, put the
output into a bucket and power it with a drill. If you get good output,
then it's downstream.

We also found out that we have about 5 minutes' cruise power with no raw
water flow: Takes that long for the fresh water loop to get hot.
Probably takes longer if you have a domestic hot water tank in the loop.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

Problem water pump Yanmar 2GM
 

Check your hoses and a part of the pump housing I believe is called the
impeller cam. It is the piece that makes the impeller deform to cause the
water to travel down stream rather than possibly stall within the pump. It
is a replaceable part and one often overlooked.
"Jeffrey P. Vasquez" wrote in
message ...
Hello all,

I recently did a standard maintenance replacement of a raw water impeller
on a Yanmar 2GM diesel. Everything seemed straightfoward, part for part,
no leakage, everything went back together straight away and test runs at
the dock were nominal.

However, during a move to a new slip the engine alarm went off. A
subsequent check revealed nothing. Took the boat out and ran the engine
for a good hour and there were no issues. The second time out the engine
alarm went off again after about the same duration of running time as the
incident during the move to the new slip.

This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

The boat is a 1989 S2.

I am stumped. Any suggestions would be infinitely appreciated.

Thanks,

Problem water pump Yanmar 2GM
 

Check your hoses and a part of the pump housing I believe is called the
impeller cam. It is the piece that makes the impeller deform to cause the
water to travel down stream rather than possibly stall within the pump. It
is a replaceable part and one often overlooked.
"Jeffrey P. Vasquez" wrote in
message ...
Hello all,

I recently did a standard maintenance replacement of a raw water impeller
on a Yanmar 2GM diesel. Everything seemed straightfoward, part for part,
no leakage, everything went back together straight away and test runs at
the dock were nominal.

However, during a move to a new slip the engine alarm went off. A
subsequent check revealed nothing. Took the boat out and ran the engine
for a good hour and there were no issues. The second time out the engine
alarm went off again after about the same duration of running time as the
incident during the move to the new slip.

This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

The boat is a 1989 S2.

I am stumped. Any suggestions would be infinitely appreciated.

Thanks,

Problem water pump Yanmar 2GM
 

First things first: Jim, Roy and all who responded, thank you! To receive
such a wealth of useful information in such a short amount of time goes
so far in reducing the frustration from this issue that I can't thank
everyone enough.

You're all tops in my book and usenet continues to rule!

Now, back to my regularly scheduled issue...

"JimB" wrote in message news:...
snip
You can check most pumps by taking the cover off and turning the
engine over with the starter while holding the fuel cut-off. If the
vanes don't turn, there's a shear failure somewhere or a missing key,
and that's your problem. If they do turn - your pump is almost
certainly OK. Back to the partial blockage . . .

Additional information: (everything Roy says I experienced is exactly
what I experienced, but I'm going to throw in my diagnostics before I get
into that and maybe someone can teach me something about my clinical
method as well). I disconnected the raw water ingress into the water pump
and sea water flowed freely from the hose (after turning on the through-
hull valve). After reconnecting that, I disconnected the hose leading
from the egress of the water pump to the engine block, aimed it at the
bilge and started the motor...nothing coming out. That seemed pretty
definitive to me. (I've left out steps starting with the strainer and all
points in between and skipped to the stuff which I think was clear cut
and supports Roy's analysis).

Btw, I still haven't found the heat sensor; the Yanmar book isn't
particularly clear on some details, I haven't downloaded the S2 manual
PDF yet, etc., but the engine is definitely hot. And it's raw water, not
fresh water (as I understand it).

Have fun. Maybe someone who knows your Yanmar will give you a better
story.

Fun I did not have. Vessel Assist I did have. =)


(Roy G. Biv) wrote:
I had a VERY frustrating overheating problem, sounds VERY similar to
what Jeff describes and Jim has Almost focused on what the problem
was . For me it was very frustrating, check strainer, check hoses,
check impeller, (still overheats) check pump (ok), pull exhaust
(still overheats), replace w new impeller (still overheats) put in 2nd
new impeller (still overheats) damn thing would run FINE at idle in
the canal, when I get out the channel and pick up rpm it would
overheat., seastrainer clear from beginning, no air leaks.

take pump cover off, R&R impeller & never find anything wrong. Put it
back together and runs fine at idle. (sound familiar Jeff?)

Finally I discovered what was happening was what Jim alluded to -- a
shear failure. Where the pulley fits on the water pump shaft was the
problem. There was enough drag to (pump off engine) to turn the pulley
by hand and observe the shaft spin & impeller turn (offering NO CLUE
because it APPEARED to be OK). Under load the drag was overcome and
EVEN THOUGH I could see the belt spinning the pulley, the drag on the
impeller overcame the shaft/pulley drag .

The problem was Both the pulley and the shaft, couldn't just relace
the pulley had to replace the shaft, to replace the shaft needed new
bearings and seals & by the time you add the shaft, bearings, seals, &
pulley together as a parts order it made more sense (cents!) to just
buy a new pump assembly (not cheap either)

Okay, not just *very* familiar, but spot on exact. However, if I am
understanding your description, it seems you were in the act of
rebuilding or partially rebuilding the water pump prior to the fault? Is
it possible that simply opening the back plate, removing the worn
impeller (worn, but no missing vanes), installing a new impeller,
replacing the gasket and replacing the backplate could result in the
sudden occurrence of this shear issue? Could the friction generated by
the fresh rubber of the new impeller (and possible dry running, though
the engine manual says dry-running will destroy the impeller in seconds,
which it didn't or wasn't) have caused a shear issue between pulley and
shaft where none existed before?

I have read that water flows through the water pump without rotation of
the impeller. I note that in my case there is no positive seal within the
water pump housing and impeller, is this correct? It seems
counterintuitive to me with the whole function of the rubber vanes and
the cam within the pump, so maybe I'm just having trouble grasping its
operation.

There is some slight scoring on the backplate, but it's extremely
minimal. If there's no positive seal within the pumping mechanism, what
does the scoring affect, other than friction?

I think I've bypassed the issue of plugged outlet downstream from the
pump (though there is so much downstream of the pump I am confident there
will be plenty of opportunity for the suggested blockage to happen in the
near future) by disconnecting the feed directly from the water pump and
into the engine block and running the engine. Is it possible this is not
as well-defined as I'm leading myself to believe?

Again, thank you all! This was demoralizing to have what seems such a
minor piece of hardware and rudimentary technology present such a huge
issue and it was very heartening to hear Roy's story on how pernicious
the issue could really be.

Deepest regards,

[Cool sailing-related .sig here when I are a real sailor]

Problem water pump Yanmar 2GM
 

First things first: Jim, Roy and all who responded, thank you! To receive
such a wealth of useful information in such a short amount of time goes
so far in reducing the frustration from this issue that I can't thank
everyone enough.

You're all tops in my book and usenet continues to rule!

Now, back to my regularly scheduled issue...

"JimB" wrote in message news:...
snip
You can check most pumps by taking the cover off and turning the
engine over with the starter while holding the fuel cut-off. If the
vanes don't turn, there's a shear failure somewhere or a missing key,
and that's your problem. If they do turn - your pump is almost
certainly OK. Back to the partial blockage . . .

Additional information: (everything Roy says I experienced is exactly
what I experienced, but I'm going to throw in my diagnostics before I get
into that and maybe someone can teach me something about my clinical
method as well). I disconnected the raw water ingress into the water pump
and sea water flowed freely from the hose (after turning on the through-
hull valve). After reconnecting that, I disconnected the hose leading
from the egress of the water pump to the engine block, aimed it at the
bilge and started the motor...nothing coming out. That seemed pretty
definitive to me. (I've left out steps starting with the strainer and all
points in between and skipped to the stuff which I think was clear cut
and supports Roy's analysis).

Btw, I still haven't found the heat sensor; the Yanmar book isn't
particularly clear on some details, I haven't downloaded the S2 manual
PDF yet, etc., but the engine is definitely hot. And it's raw water, not
fresh water (as I understand it).

Have fun. Maybe someone who knows your Yanmar will give you a better
story.

Fun I did not have. Vessel Assist I did have. =)


(Roy G. Biv) wrote:
I had a VERY frustrating overheating problem, sounds VERY similar to
what Jeff describes and Jim has Almost focused on what the problem
was . For me it was very frustrating, check strainer, check hoses,
check impeller, (still overheats) check pump (ok), pull exhaust
(still overheats), replace w new impeller (still overheats) put in 2nd
new impeller (still overheats) damn thing would run FINE at idle in
the canal, when I get out the channel and pick up rpm it would
overheat., seastrainer clear from beginning, no air leaks.

take pump cover off, R&R impeller & never find anything wrong. Put it
back together and runs fine at idle. (sound familiar Jeff?)

Finally I discovered what was happening was what Jim alluded to -- a
shear failure. Where the pulley fits on the water pump shaft was the
problem. There was enough drag to (pump off engine) to turn the pulley
by hand and observe the shaft spin & impeller turn (offering NO CLUE
because it APPEARED to be OK). Under load the drag was overcome and
EVEN THOUGH I could see the belt spinning the pulley, the drag on the
impeller overcame the shaft/pulley drag .

The problem was Both the pulley and the shaft, couldn't just relace
the pulley had to replace the shaft, to replace the shaft needed new
bearings and seals & by the time you add the shaft, bearings, seals, &
pulley together as a parts order it made more sense (cents!) to just
buy a new pump assembly (not cheap either)

Okay, not just *very* familiar, but spot on exact. However, if I am
understanding your description, it seems you were in the act of
rebuilding or partially rebuilding the water pump prior to the fault? Is
it possible that simply opening the back plate, removing the worn
impeller (worn, but no missing vanes), installing a new impeller,
replacing the gasket and replacing the backplate could result in the
sudden occurrence of this shear issue? Could the friction generated by
the fresh rubber of the new impeller (and possible dry running, though
the engine manual says dry-running will destroy the impeller in seconds,
which it didn't or wasn't) have caused a shear issue between pulley and
shaft where none existed before?

I have read that water flows through the water pump without rotation of
the impeller. I note that in my case there is no positive seal within the
water pump housing and impeller, is this correct? It seems
counterintuitive to me with the whole function of the rubber vanes and
the cam within the pump, so maybe I'm just having trouble grasping its
operation.

There is some slight scoring on the backplate, but it's extremely
minimal. If there's no positive seal within the pumping mechanism, what
does the scoring affect, other than friction?

I think I've bypassed the issue of plugged outlet downstream from the
pump (though there is so much downstream of the pump I am confident there
will be plenty of opportunity for the suggested blockage to happen in the
near future) by disconnecting the feed directly from the water pump and
into the engine block and running the engine. Is it possible this is not
as well-defined as I'm leading myself to believe?

Again, thank you all! This was demoralizing to have what seems such a
minor piece of hardware and rudimentary technology present such a huge
issue and it was very heartening to hear Roy's story on how pernicious
the issue could really be.

Deepest regards,

[Cool sailing-related .sig here when I are a real sailor]

Problem water pump Yanmar 2GM
 

"The Carrolls" wrote:
Check your hoses and a part of the pump housing I believe is called
the impeller cam. It is the piece that makes the impeller deform to
cause the water to travel down stream rather than possibly stall
within the pump. It is a replaceable part and one often overlooked.

Thanks Jere and the Carrolls! It is profoundly encouraging to have such
quick and helpful responses. My thanks.

[This was cross-posted to rec.boats.cruising and a fellow usenetter there
wrote up an extremely good summary of shaft/pulley shear resulting in
exactly these symptoms, if you'd like to hop over there and read it.]

Thanks again!!

Problem water pump Yanmar 2GM
 

"The Carrolls" wrote:
Check your hoses and a part of the pump housing I believe is called
the impeller cam. It is the piece that makes the impeller deform to
cause the water to travel down stream rather than possibly stall
within the pump. It is a replaceable part and one often overlooked.

Thanks Jere and the Carrolls! It is profoundly encouraging to have such
quick and helpful responses. My thanks.

[This was cross-posted to rec.boats.cruising and a fellow usenetter there
wrote up an extremely good summary of shaft/pulley shear resulting in
exactly these symptoms, if you'd like to hop over there and read it.]

Thanks again!!

Problem water pump Yanmar 2GM
 

In article ,
"Jeffrey P. Vasquez"
wrote:

Hello all,

I recently did a standard maintenance replacement of a raw water impeller
on a Yanmar 2GM diesel. Everything seemed straightfoward, part for part,
no leakage, everything went back together straight away and test runs at
the dock were nominal.

However, during a move to a new slip the engine alarm went off. A
subsequent check revealed nothing. Took the boat out and ran the engine
for a good hour and there were no issues. The second time out the engine
alarm went off again after about the same duration of running time as the
incident during the move to the new slip.

This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

The boat is a 1989 S2.

I am stumped. Any suggestions would be infinitely appreciated.

Thanks,

One thing to check isif the shaft that drives the impeller is in one
piece. I had a JABSCO where the shaft was made in two parts that were
pressfit together. Water leaked thru a failed seal and corroded the
shaft connection to the point that the pressfit connection failed.
Pully turned, but impeller didn't. I found it by turning over the
engine with the pump faceplate off and watching the impeller itself.

Bruce in alaska
--
add a 2 before @

Problem water pump Yanmar 2GM
 

In article ,
"Jeffrey P. Vasquez"
wrote:

Hello all,

I recently did a standard maintenance replacement of a raw water impeller
on a Yanmar 2GM diesel. Everything seemed straightfoward, part for part,
no leakage, everything went back together straight away and test runs at
the dock were nominal.

However, during a move to a new slip the engine alarm went off. A
subsequent check revealed nothing. Took the boat out and ran the engine
for a good hour and there were no issues. The second time out the engine
alarm went off again after about the same duration of running time as the
incident during the move to the new slip.

This time there was no curing it. I dismantled everything upstream and
downstream of the water pump and it appears there is no flow through the
water pump even though everything appears to be functioning exactly as
it's supposed to. The impeller is fine, the belt tension and pulley
function are fine and there are no blockages from the through-hull to its
egress.

The boat is a 1989 S2.

I am stumped. Any suggestions would be infinitely appreciated.

Thanks,

One thing to check isif the shaft that drives the impeller is in one
piece. I had a JABSCO where the shaft was made in two parts that were
pressfit together. Water leaked thru a failed seal and corroded the
shaft connection to the point that the pressfit connection failed.
Pully turned, but impeller didn't. I found it by turning over the
engine with the pump faceplate off and watching the impeller itself.

Bruce in alaska
--
add a 2 before @

Problem water pump Yanmar 2GM
 

Older Yanmar pumps have trouble keeping the pressure up to maintain
the flow unless the pump clearances are correct. This is more of a
problem on boats with hot water heaters, engine driven refrigeration
and water-lift exhausts.

When replacing the raw water pump impeller it is important to check
the clearance between the parting surface and the impeller. Make sure
the impeller is all the way in the pump then with a straight edge and
a feeler gauge check the free clearance of .001 to .002 of an inch. If
there are too gaskets on the pump plate instead of the thin one
supplied by Yanmar, pumping pressure will be effected.

On 2GM and 3GM engines that are salt water cooled a stuck closed or
missing thermostat will bypass the water all the time causing the
engine to overheat.

From the author of four books on boat refrigeration.
http://www.kollmann-marine.com

Problem water pump Yanmar 2GM
 

Older Yanmar pumps have trouble keeping the pressure up to maintain
the flow unless the pump clearances are correct. This is more of a
problem on boats with hot water heaters, engine driven refrigeration
and water-lift exhausts.

When replacing the raw water pump impeller it is important to check
the clearance between the parting surface and the impeller. Make sure
the impeller is all the way in the pump then with a straight edge and
a feeler gauge check the free clearance of .001 to .002 of an inch. If
there are too gaskets on the pump plate instead of the thin one
supplied by Yanmar, pumping pressure will be effected.

On 2GM and 3GM engines that are salt water cooled a stuck closed or
missing thermostat will bypass the water all the time causing the
engine to overheat.

From the author of four books on boat refrigeration.
http://www.kollmann-marine.com

Problem water pump Yanmar 2GM
 

On Sun, 04 Jan 2004 19:29:28 GMT, "Jeffrey P. Vasquez"
wrote:


"The Carrolls" wrote:
Check your hoses and a part of the pump housing I believe is called
the impeller cam. It is the piece that makes the impeller deform to
cause the water to travel down stream rather than possibly stall
within the pump. It is a replaceable part and one often overlooked.

Thanks Jere and the Carrolls! It is profoundly encouraging to have such
quick and helpful responses. My thanks.

[This was cross-posted to rec.boats.cruising and a fellow usenetter there
wrote up an extremely good summary of shaft/pulley shear resulting in
exactly these symptoms, if you'd like to hop over there and read it.]

Thanks again!!


I had one impeller fail by the rubber coming adrift from the metal
bushing - everything looked fine, but the rubber didn't turn.




--
Peter Bennett, VE7CEI
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

Problem water pump Yanmar 2GM
 

On Sun, 04 Jan 2004 19:29:28 GMT, "Jeffrey P. Vasquez"
wrote:


"The Carrolls" wrote:
Check your hoses and a part of the pump housing I believe is called
the impeller cam. It is the piece that makes the impeller deform to
cause the water to travel down stream rather than possibly stall
within the pump. It is a replaceable part and one often overlooked.

Thanks Jere and the Carrolls! It is profoundly encouraging to have such
quick and helpful responses. My thanks.

[This was cross-posted to rec.boats.cruising and a fellow usenetter there
wrote up an extremely good summary of shaft/pulley shear resulting in
exactly these symptoms, if you'd like to hop over there and read it.]

Thanks again!!


I had one impeller fail by the rubber coming adrift from the metal
bushing - everything looked fine, but the rubber didn't turn.




--
Peter Bennett, VE7CEI
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

Problem water pump Yanmar 2GM
 

On Sun, 04 Jan 2004 19:13:50 GMT, "Jeffrey P. Vasquez"
wrote:



Additional information: (everything Roy says I experienced is exactly
what I experienced, but I'm going to throw in my diagnostics before I get
into that and maybe someone can teach me something about my clinical
method as well). I disconnected the raw water ingress into the water pump
and sea water flowed freely from the hose (after turning on the through-
hull valve). After reconnecting that, I disconnected the hose leading
from the egress of the water pump to the engine block, aimed it at the
bilge and started the motor...nothing coming out. That seemed pretty
definitive to me. (I've left out steps starting with the strainer and all
points in between and skipped to the stuff which I think was clear cut
and supports Roy's analysis).

Btw, I still haven't found the heat sensor; the Yanmar book isn't
particularly clear on some details, I haven't downloaded the S2 manual
PDF yet, etc., but the engine is definitely hot. And it's raw water, not
fresh water (as I understand it).

I may be misunderstanding you here. There is no difficulty telling
visually whether a yanmar is raw cooled or fresh. the heat exchanger
in the fresh-water-cooled engines is a rectangular tank above and to
the right of the cylinder head with a radiator cap in it. It has four
hoses, in and out for both raw and fresh water.

A raw cooled engine does not have this at all.




Rodney Myrvaagnes J36 Gjo/a


Does one child rape really change Strom Thurmond's lifetime record?
For better or worse?

Problem water pump Yanmar 2GM
 

On Sun, 04 Jan 2004 19:13:50 GMT, "Jeffrey P. Vasquez"
wrote:



Additional information: (everything Roy says I experienced is exactly
what I experienced, but I'm going to throw in my diagnostics before I get
into that and maybe someone can teach me something about my clinical
method as well). I disconnected the raw water ingress into the water pump
and sea water flowed freely from the hose (after turning on the through-
hull valve). After reconnecting that, I disconnected the hose leading
from the egress of the water pump to the engine block, aimed it at the
bilge and started the motor...nothing coming out. That seemed pretty
definitive to me. (I've left out steps starting with the strainer and all
points in between and skipped to the stuff which I think was clear cut
and supports Roy's analysis).

Btw, I still haven't found the heat sensor; the Yanmar book isn't
particularly clear on some details, I haven't downloaded the S2 manual
PDF yet, etc., but the engine is definitely hot. And it's raw water, not
fresh water (as I understand it).

I may be misunderstanding you here. There is no difficulty telling
visually whether a yanmar is raw cooled or fresh. the heat exchanger
in the fresh-water-cooled engines is a rectangular tank above and to
the right of the cylinder head with a radiator cap in it. It has four
hoses, in and out for both raw and fresh water.

A raw cooled engine does not have this at all.




Rodney Myrvaagnes J36 Gjo/a


Does one child rape really change Strom Thurmond's lifetime record?
For better or worse?

Problem water pump Yanmar 2GM
 

Rodney wrote:
I may be misunderstanding you here. There is no difficulty telling
visually whether a yanmar is raw cooled or fresh. the heat exchanger
in the fresh-water-cooled engines is a rectangular tank above and to
the right of the cylinder head with a radiator cap in it. It has four
hoses, in and out for both raw and fresh water.

A raw cooled engine does not have this at all.

Yes, it's raw. I always leave the door open to be enlightened when I know I
am not an expert.

Problem water pump Yanmar 2GM
 

Rodney wrote:
I may be misunderstanding you here. There is no difficulty telling
visually whether a yanmar is raw cooled or fresh. the heat exchanger
in the fresh-water-cooled engines is a rectangular tank above and to
the right of the cylinder head with a radiator cap in it. It has four
hoses, in and out for both raw and fresh water.

A raw cooled engine does not have this at all.

Yes, it's raw. I always leave the door open to be enlightened when I know I
am not an expert.

Problem water pump Yanmar 2GM
 

"Jeffrey P. Vasquez" wrote in
message . 17...


Your diagnositcs seem to point clearly at a pump issue. More further on -

Okay, not just *very* familiar, but spot on exact. However, if I am
understanding your description, it seems you were in the act of
rebuilding or partially rebuilding the water pump prior to the fault? Is
it possible that simply opening the back plate, removing the worn
impeller (worn, but no missing vanes), installing a new impeller,
replacing the gasket and replacing the backplate could result in the
sudden occurrence of this shear issue? Could the friction generated by
the fresh rubber of the new impeller (and possible dry running, though
the engine manual says dry-running will destroy the impeller in seconds,
which it didn't or wasn't) have caused a shear issue between pulley and
shaft where none existed before?

Possibly.

You didn't mention removing the cam, so I'm assuming that's still in place.

Depends on your gasket thickness, the length of your replacement
impeller, and how stiff it is on the shaft.

Too long an impeller, or too thin a gasket (or both!) can cause
the impeller ends to seize against the cover plate once the cover is
tightened up. At the next start, the shear occurs.

Also, if the impeller is a very tight fit on the shaft, it may be pushed in
too hard and jammed against the back plate, or it may be standing a little
too proud and jamming against the front plate. At the next start . . .

Missing out a gasket obviously also has the same effect.

With a raw water only system you'd overheat pretty quickly. Your test
separating the pipe at the engine block and seeing no water entering the
block eliminates the most common blockage problem, which is the slow build
up of calcium and borate salts in that areas which regularly cycle through
hot and cold. Also, this type of build up is over the years, not days!

Sorry you're not having fun! Barked knuckles, hacksaw mashed screw slots,
lost screws in the bilge drains and used diesel oil deodorant and finger
colouring does all seem to be all part of the game. No wonder my wife tells
me not to hand the bread to our visitors!


I have read that water flows through the water pump without rotation of
the impeller.

Not significantly. You'll get a drip rate around the backplate and endplate
if there's a positive pressure, more with wear. Any more and the gasket's
too thick or the impeller too short (opposite to the seizure problem). This
leakage is trivial compared to the pumping capacity of the vanes.
--
JimB
Yacht Rapaz, sadly for sale:
http://homepage.ntlworld.com/jim.bae...cification.htm
jim(dot)baerselman(at)ntlworld(dot)com

Problem water pump Yanmar 2GM
 

"Jeffrey P. Vasquez" wrote in
message . 17...


Your diagnositcs seem to point clearly at a pump issue. More further on -

Okay, not just *very* familiar, but spot on exact. However, if I am
understanding your description, it seems you were in the act of
rebuilding or partially rebuilding the water pump prior to the fault? Is
it possible that simply opening the back plate, removing the worn
impeller (worn, but no missing vanes), installing a new impeller,
replacing the gasket and replacing the backplate could result in the
sudden occurrence of this shear issue? Could the friction generated by
the fresh rubber of the new impeller (and possible dry running, though
the engine manual says dry-running will destroy the impeller in seconds,
which it didn't or wasn't) have caused a shear issue between pulley and
shaft where none existed before?

Possibly.

You didn't mention removing the cam, so I'm assuming that's still in place.

Depends on your gasket thickness, the length of your replacement
impeller, and how stiff it is on the shaft.

Too long an impeller, or too thin a gasket (or both!) can cause
the impeller ends to seize against the cover plate once the cover is
tightened up. At the next start, the shear occurs.

Also, if the impeller is a very tight fit on the shaft, it may be pushed in
too hard and jammed against the back plate, or it may be standing a little
too proud and jamming against the front plate. At the next start . . .

Missing out a gasket obviously also has the same effect.

With a raw water only system you'd overheat pretty quickly. Your test
separating the pipe at the engine block and seeing no water entering the
block eliminates the most common blockage problem, which is the slow build
up of calcium and borate salts in that areas which regularly cycle through
hot and cold. Also, this type of build up is over the years, not days!

Sorry you're not having fun! Barked knuckles, hacksaw mashed screw slots,
lost screws in the bilge drains and used diesel oil deodorant and finger
colouring does all seem to be all part of the game. No wonder my wife tells
me not to hand the bread to our visitors!


I have read that water flows through the water pump without rotation of
the impeller.

Not significantly. You'll get a drip rate around the backplate and endplate
if there's a positive pressure, more with wear. Any more and the gasket's
too thick or the impeller too short (opposite to the seizure problem). This
leakage is trivial compared to the pumping capacity of the vanes.
--
JimB
Yacht Rapaz, sadly for sale:
http://homepage.ntlworld.com/jim.bae...cification.htm
jim(dot)baerselman(at)ntlworld(dot)com

Problem water pump Yanmar 2GM
 

another problem I have seen on yanmar model 2qm15 is that the Zinc
mounting housing (Salt/raw water cooled) has the hose from the water
pump to the zinc housing mounted in a verticle orientation with the hose
from water pump to zinc housing coming from underneath the zincs house.
When replacing the original hoses I found the zinc had built up a crust
inside the hose under the zinc housing to the point where the hose was
becoming constricted by the build up, might as well replace your zincs
and check for that .

"Jeffrey P. Vasquez" wrote in message news:...

Yes, it's raw.

Problem water pump Yanmar 2GM
 

another problem I have seen on yanmar model 2qm15 is that the Zinc
mounting housing (Salt/raw water cooled) has the hose from the water
pump to the zinc housing mounted in a verticle orientation with the hose
from water pump to zinc housing coming from underneath the zincs house.
When replacing the original hoses I found the zinc had built up a crust
inside the hose under the zinc housing to the point where the hose was
becoming constricted by the build up, might as well replace your zincs
and check for that .

"Jeffrey P. Vasquez" wrote in message news:...

Yes, it's raw.

I've had the same problems with my water pump on my 2GM and three different engineers have thought that the hoses had delaminated, the anti syphon valve had failed or the thermostat had seized. All things that I'd checked anyhow.
It runs from cold for as long as I want pumping water from the back but as soon as I shut it down, sail for a bit and then start it up the pump fails.
My thinking was this - the cam and inside face of the pump have worn enough from sand/silt that a warm engine creates a pressure differential in the cooling system to prevent a failing/failed pump to pump - but running from cold the cooling system, once pumping, will syphon.
However, the notion of the pulley spinning on the spindle (above) also works in my mind, i.e. the pump works and syphons from cold but a hot (and expanded) pulley will not pump although visually all looks good.
I'll check the pulley at the weekend but regardless I'm buying a new pump.
But, here's the thing. A replacement raw pump - about 40 litres a minute costs £366 but a freshwater pump (exactly the same mounts but a bigger impeller) costs £120 and pumps around 50 litres a minute.
I'm sure that the thermostat will regulate the flow through the engine anyway, but has anybody got any experience of increasing the flow in this way? I spoke to Yanmar UK and they told me to fit the raw water pump but had no advice regarding the freshwater pump.