I have a 350 with an Alpha 1 that is overheating at low rpms. Diagnosing
the same problem last year, I had to have the water pump in the lower unit
replaced. I will troubleshoot all other possibilities this weekend before
having to pull the boat out, but thought you folks in the news groups may
have some ideas as to what other causes it could be.

The boat is an 86 and I have owned it for about ten years for having to
replace the outdrive water pump. Any estimates as to what the life
expectancy of the water pump should be?

First I will be checking for leaks, then changing the t'stat on the engine
(as I do not recall when I last replaced it), but beyond that, Ican only
suspect either the new (last year) pump has failed prematurely, or the
mechanic I hired to do it did.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

Sorry I don't have the reference, but 3 years or so is the "recommended"
impeller replacement schedule. And that I think is based on a 100 hours or
so season. I also understand that the newer impellers are built to last
longer. My approach ... pull the outdrive every 3 seasons to lube the
u-joints etc, and while it's off replace the impeller. And then there are
people run their boats 10 years with no preventive maintenance and have no
problems :-)

"Mark" wrote in message
sgroups.com...
I have a 350 with an Alpha 1 that is overheating at low rpms. Diagnosing
the same problem last year, I had to have the water pump in the lower unit
replaced. I will troubleshoot all other possibilities this weekend
before
having to pull the boat out, but thought you folks in the news groups may
have some ideas as to what other causes it could be.

The boat is an 86 and I have owned it for about ten years for having to
replace the outdrive water pump. Any estimates as to what the life
expectancy of the water pump should be?

First I will be checking for leaks, then changing the t'stat on the engine
(as I do not recall when I last replaced it), but beyond that, Ican only
suspect either the new (last year) pump has failed prematurely, or the
mechanic I hired to do it did.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

Oops ... I read "water pump" as the engine water pump, not impeller. If it
was me, I'd pull the boat out and hook up the muffs and garden hose. Could
be someone started the engine up with no water supply ... that burns out the
impeller. Or could be the engine water pump, or risers blocked, or
thermostat, or .... could even be a faulty temperature gauge. Anyway,
running it on the garden hose should give some insight into the problem.

Agreed on the engine pump, this is the most typical cause of low RPM over
heating and OK at higher. It isn't a displacement pump like the one on the
drive, it is a centrifugal pump and as it ages, the vanes corrode off, they
simply don't sling any water at low speeds then. End result is lots of
water from driver pump, however it isn't circulated through the block, it
just get poured out the exhaust. The engine pump is responsible to move it
through the block and heads.

Common issue on cars with high mileage also, overheat at idle, OK if revved
up a bit..

Greg

"Bowgus" wrote in message
...
Oops ... I read "water pump" as the engine water pump, not impeller. If
it
was me, I'd pull the boat out and hook up the muffs and garden hose. Could
be someone started the engine up with no water supply ... that burns out
the
impeller. Or could be the engine water pump, or risers blocked, or
thermostat, or .... could even be a faulty temperature gauge. Anyway,
running it on the garden hose should give some insight into the problem.

You don't say whether you operate in fresh or salt water, or whether your
engine has fresh water w/anti-freeze circulating coolant (w/ heat
exchanger). Esp if it's operated in salt water, on a '86 boat, I'd bet on
the riser being clogged. Pull it and have a look -- you'll need new gaskets
when making replacement. You can "rod it out" or have a radiator shop give
it an acid cleaning -- either will give you just one or two seasons more.
Usually better to buy new if you intend to keep the boat.

First choice would have been lower unit pump impeller, but that's fairly
new -- unless it was later run dry and damaged. Impellers should be changed
every three years or so for normal recreational boats. The rubber gets stiff
with age and they lose efficiency. In water with lots of silt and
particulates, esp frequent shallow water operation, they can wear out faster
due to abrasion. Same for the metal contact surface in the pump --
inspection will tell if that (or more likely) the whole pump needs replaced.

Good luck,
Len

Eliminate "ns" for email address.

--
"Mark" wrote in message
sgroups.com...
I have a 350 with an Alpha 1 that is overheating at low rpms. Diagnosing
the same problem last year, I had to have the water pump in the lower unit
replaced. I will troubleshoot all other possibilities this weekend
before
having to pull the boat out, but thought you folks in the news groups may
have some ideas as to what other causes it could be.

The boat is an 86 and I have owned it for about ten years for having to
replace the outdrive water pump. Any estimates as to what the life
expectancy of the water pump should be?

First I will be checking for leaks, then changing the t'stat on the engine
(as I do not recall when I last replaced it), but beyond that, Ican only
suspect either the new (last year) pump has failed prematurely, or the
mechanic I hired to do it did.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

On Fri, 3 Jun 2005 07:37:16 -0400, "Mark"
wrote:

I have a 350 with an Alpha 1 that is overheating at low rpms.

Dont worry about it, its probably the gauge.

Me and the wife
http://pg.photos.yahoo.com/ph/harkra...bum?.dir=/1323

Harry.Krause wrote:
On Fri, 3 Jun 2005 07:37:16 -0400, "Mark"
wrote:


I have a 350 with an Alpha 1 that is overheating at low rpms.


Dont worry about it, its probably the gauge.

Me and the wife
http://pg.photos.yahoo.com/ph/harkra...bum?.dir=/1323


You really shouldn't give out silly advice and credit it to another
poster. It could cause some unsuspecting poster substantial money.

I am running in fresh water (St. Lawrence 1000 Islands area) and it is not a
closed system (no antifreeze). My boating habits rarely take me into silty
/ dirty water, but maybe the zebra mussels that have invaded the area and
cleaned up the water have managed to get hold of my system. I have never
run the boat dry and do not even turn the engine over without muffs on.
Another boating friend insists it is the pump in the outdrive that is the
trouble and has offerred to assist changing it this time.

The reason I am suspecting the outdrive pump is the "so called" mechanic
that replaced it for me last year somehow managed to reassemble the drive
without a spacer / washer that can fall out when the drive is split. That
washer missing caused no symtoms for about a month or two and then
periodically caused an inability to shift. I contacted a more reputable
mechanic and he diagnosed the problem for me over the phone and had my boat
fixed back up the same day.

Some great feedback and suggestions everyone.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

"Len Krauss" wrote in message
...
You don't say whether you operate in fresh or salt water, or whether your
engine has fresh water w/anti-freeze circulating coolant (w/ heat
exchanger). Esp if it's operated in salt water, on a '86 boat, I'd bet on
the riser being clogged. Pull it and have a look -- you'll need new
gaskets
when making replacement. You can "rod it out" or have a radiator shop give
it an acid cleaning -- either will give you just one or two seasons more.
Usually better to buy new if you intend to keep the boat.

First choice would have been lower unit pump impeller, but that's fairly
new -- unless it was later run dry and damaged. Impellers should be
changed
every three years or so for normal recreational boats. The rubber gets
stiff
with age and they lose efficiency. In water with lots of silt and
particulates, esp frequent shallow water operation, they can wear out
faster
due to abrasion. Same for the metal contact surface in the pump --
inspection will tell if that (or more likely) the whole pump needs
replaced.

Good luck,
Len

Eliminate "ns" for email address.

--
"Mark" wrote in message
sgroups.com...
I have a 350 with an Alpha 1 that is overheating at low rpms.
Diagnosing
the same problem last year, I had to have the water pump in the lower
unit
replaced. I will troubleshoot all other possibilities this weekend
before
having to pull the boat out, but thought you folks in the news groups may
have some ideas as to what other causes it could be.

The boat is an 86 and I have owned it for about ten years for having to
replace the outdrive water pump. Any estimates as to what the life
expectancy of the water pump should be?

First I will be checking for leaks, then changing the t'stat on the
engine
(as I do not recall when I last replaced it), but beyond that, Ican only
suspect either the new (last year) pump has failed prematurely, or the
mechanic I hired to do it did.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

I am making progress with my over heating problem! Getting ready to pull
the boat to change the outdrive impeller, the folks at Gilbert Marine in
Brockville suggested I try pulling the hose going into the housing near the
thermostat (coming from the outdrive) and run the engine just long enough to
see if and how much water the impeller is pushing up. Estimating maybe a
gallon in 5 to 10 seconds, I felt that should be sufficient and moved onto
the next possibility (and much easier than splitting the outdrive to change
the water pump). I removed the t'stat and ran the engine at idle and
higher rpms and the temperature never went over 135 (normally operates
around 145 to 150). I am going to try it this weekend with no thermostat
and see what happens. Stay tuned ...

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm (link to the company website describing my
accessory hooks for boats)


"Mark" wrote in message
sgroups.com...
I am running in fresh water (St. Lawrence 1000 Islands area) and it is not
a closed system (no antifreeze). My boating habits rarely take me into
silty / dirty water, but maybe the zebra mussels that have invaded the area
and cleaned up the water have managed to get hold of my system. I have
never run the boat dry and do not even turn the engine over without muffs
on. Another boating friend insists it is the pump in the outdrive that is
the trouble and has offerred to assist changing it this time.

The reason I am suspecting the outdrive pump is the "so called" mechanic
that replaced it for me last year somehow managed to reassemble the drive
without a spacer / washer that can fall out when the drive is split.
That washer missing caused no symtoms for about a month or two and then
periodically caused an inability to shift. I contacted a more reputable
mechanic and he diagnosed the problem for me over the phone and had my
boat fixed back up the same day.

Some great feedback and suggestions everyone.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

"Len Krauss" wrote in message
...
You don't say whether you operate in fresh or salt water, or whether your
engine has fresh water w/anti-freeze circulating coolant (w/ heat
exchanger). Esp if it's operated in salt water, on a '86 boat, I'd bet
on
the riser being clogged. Pull it and have a look -- you'll need new
gaskets
when making replacement. You can "rod it out" or have a radiator shop
give
it an acid cleaning -- either will give you just one or two seasons more.
Usually better to buy new if you intend to keep the boat.

First choice would have been lower unit pump impeller, but that's fairly
new -- unless it was later run dry and damaged. Impellers should be
changed
every three years or so for normal recreational boats. The rubber gets
stiff
with age and they lose efficiency. In water with lots of silt and
particulates, esp frequent shallow water operation, they can wear out
faster
due to abrasion. Same for the metal contact surface in the pump --
inspection will tell if that (or more likely) the whole pump needs
replaced.

Good luck,
Len

Eliminate "ns" for email address.

--
"Mark" wrote in message
sgroups.com...
I have a 350 with an Alpha 1 that is overheating at low rpms. Diagnosing
the same problem last year, I had to have the water pump in the lower
unit
replaced. I will troubleshoot all other possibilities this weekend
before
having to pull the boat out, but thought you folks in the news groups
may
have some ideas as to what other causes it could be.

The boat is an 86 and I have owned it for about ten years for having to
replace the outdrive water pump. Any estimates as to what the life
expectancy of the water pump should be?

First I will be checking for leaks, then changing the t'stat on the
engine
(as I do not recall when I last replaced it), but beyond that, Ican only
suspect either the new (last year) pump has failed prematurely, or the
mechanic I hired to do it did.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm

A suggestion ... don't run the engine very long without a thermostat ...
even better, don't run without a thermostat at all. One of the thermostat's
function I've been told is to ensure a relatively consistent engine
temperature preventing parts warp etc.. Having said that, I had a thermostat
fail closed on a Toyota. I removed it and drove home from ... interestingly
enough Johnstown near where you're at ... to Ottawa without any apparent
problems.

I am going to try it this weekend with no thermostat and see what
happens. Stay tuned ...