Hello all,

It's me again and I've a new riddle to pose to you. It's the S2 with the
raw-water cooled Yanmar in a marine environment again. Here's the latest:

1) Through-hull has been thoroughly cleaned.
2) Raw water strainer and hoses have been replaced.
3) Water pump has been replaced.
4) Thermostat has been replaced.
5) Mixing elbow has been replaced.
6) Entire system has been "Marsolved" (marine solvent)

Here are the symptoms:

When the engine is first started there is a good flow of water through
the system as evidenced from the exhaust. The engine runs to temperature
(150F) and operates fine indefinitely with no fluctuation in temperature
at operating rpm.

After operating at temperature for some fifteen minutes (arbitrary, but
approximately the time it takes to clear the marina and channel), the
engine is stopped and allowed to cool. After cooling the engine is
restarted and no flow of water is observed as evidenced by the exhaust.
Running at idle or at operating rpm does not alter the condition and the
engine heats to alarm. This has been confirmed in absence of sailing,
i.e. a siphon break was suspected (and may have been a past culprit), so
the hoses were rerouted to ensure positive pressure to the water pump
when the boat is level.

If the system is disassembled upstream to downstream (after cooling
sufficient to touch), flow through it at all points is observed. If the
system is reassembled it will at this point again function properly.

I would liken this behavior to vapor lock in automobile fuel systems, but
I have no understanding how this would be relevant to the Yanmar cooling
system.

The mechanic's diagnosis is blockage in the engine block itself and the
suggested recommendation is replace the entire engine.

Any opinions, experience, recommendations or wild-eyed guesses would be
infinitely appreciated as always. If engine replacement is the correct
course of action, what does one do with a Yanmar 2GM with about 1800
hours and a suspected cooling blockage?

Many thanks!

1 Never ever beleive a mechanic when he mentions Large Amount of Cash
to replace the engine is the solution.

2. After the flow stops and the engine cools sufficient to work on it.
Remove the outlet water hose from the exhaust manifold and see if there
is water flow. If not flow, remove the inlet hose to the exhaust
manifold to see if there is flow, if flow at the inlet and not at the
outlet ..... remove the exhaust manifold and poke inside with a stiff
wire to break up all the 'platelette' rust slabs. Turn the manifold
upside down and shake out all the debris. Cast iron manifolds are
vulnerable to "slab rust" and occasionally the loose slabs
intermittantly block the passages.

A Yanmar with 1800 hrs. on it ........ isnt fully 'broken in".
Hope this helps




In article , Jeffrey P.
Vasquez wrote:

Hello all,

It's me again and I've a new riddle to pose to you. It's the S2 with the
raw-water cooled Yanmar in a marine environment again. Here's the latest:

1) Through-hull has been thoroughly cleaned.
2) Raw water strainer and hoses have been replaced.
3) Water pump has been replaced.
4) Thermostat has been replaced.
5) Mixing elbow has been replaced.
6) Entire system has been "Marsolved" (marine solvent)

Here are the symptoms:

When the engine is first started there is a good flow of water through
the system as evidenced from the exhaust. The engine runs to temperature
(150F) and operates fine indefinitely with no fluctuation in temperature
at operating rpm.

After operating at temperature for some fifteen minutes (arbitrary, but
approximately the time it takes to clear the marina and channel), the
engine is stopped and allowed to cool. After cooling the engine is
restarted and no flow of water is observed as evidenced by the exhaust.
Running at idle or at operating rpm does not alter the condition and the
engine heats to alarm. This has been confirmed in absence of sailing,
i.e. a siphon break was suspected (and may have been a past culprit), so
the hoses were rerouted to ensure positive pressure to the water pump
when the boat is level.

If the system is disassembled upstream to downstream (after cooling
sufficient to touch), flow through it at all points is observed. If the
system is reassembled it will at this point again function properly.

I would liken this behavior to vapor lock in automobile fuel systems, but
I have no understanding how this would be relevant to the Yanmar cooling
system.

The mechanic's diagnosis is blockage in the engine block itself and the
suggested recommendation is replace the entire engine.

Any opinions, experience, recommendations or wild-eyed guesses would be
infinitely appreciated as always. If engine replacement is the correct
course of action, what does one do with a Yanmar 2GM with about 1800
hours and a suspected cooling blockage?

Many thanks!

When the engine is running and about to overheat, have you pulled the hose after
the waterpump to see if there's any flow?

BTW, a friend just replaced a 2GM with the new Yanmar (2YM or something like
that?). cost was over $7K for the engine, under $2K for the installation. He
hopes to get around $1K for the old engine, which runs but burns oil.



"Jeffrey P. Vasquez" wrote in
message ...
Hello all,

It's me again and I've a new riddle to pose to you. It's the S2 with the
raw-water cooled Yanmar in a marine environment again. Here's the latest:

1) Through-hull has been thoroughly cleaned.
2) Raw water strainer and hoses have been replaced.
3) Water pump has been replaced.
4) Thermostat has been replaced.
5) Mixing elbow has been replaced.
6) Entire system has been "Marsolved" (marine solvent)

Here are the symptoms:

When the engine is first started there is a good flow of water through
the system as evidenced from the exhaust. The engine runs to temperature
(150F) and operates fine indefinitely with no fluctuation in temperature
at operating rpm.

After operating at temperature for some fifteen minutes (arbitrary, but
approximately the time it takes to clear the marina and channel), the
engine is stopped and allowed to cool. After cooling the engine is
restarted and no flow of water is observed as evidenced by the exhaust.
Running at idle or at operating rpm does not alter the condition and the
engine heats to alarm. This has been confirmed in absence of sailing,
i.e. a siphon break was suspected (and may have been a past culprit), so
the hoses were rerouted to ensure positive pressure to the water pump
when the boat is level.

If the system is disassembled upstream to downstream (after cooling
sufficient to touch), flow through it at all points is observed. If the
system is reassembled it will at this point again function properly.

I would liken this behavior to vapor lock in automobile fuel systems, but
I have no understanding how this would be relevant to the Yanmar cooling
system.

The mechanic's diagnosis is blockage in the engine block itself and the
suggested recommendation is replace the entire engine.

Any opinions, experience, recommendations or wild-eyed guesses would be
infinitely appreciated as always. If engine replacement is the correct
course of action, what does one do with a Yanmar 2GM with about 1800
hours and a suspected cooling blockage?

Many thanks!

I know you've replaced it, but I've seen this caused by a defective
water pump impeller. Its really easy to ruin the Yanmar impeller - it
looks good but its seal is just bad enough that it likes to air lock.
Replacing the impeller on spec is a cheap experiment - if it fails you
have a spare :-) And make sure you put the new one in correctly, and
don't run it dry to start with.
--

I can't site any specific thing or engine part to look at/repair/replace but
your evaluation of a "vaporlock" that is thermal related is a good lead.
You can only tie down the actual cause when you can monitor the water flow
at the temperature it happens. When you wait for it to cool enough to
handle the thermal blockage has already changed and relaxed it's blockage.
What is needed is to install "Flow View Sight Glasses" in the water line(s)
to be able to visualize the amount of water flow at all times that the
engine is in operation and at all temperatures. At least one wide view sight
glass cataloged in Grainger's is rated for 130 PSI @ 212° F so that they are
safe to install in the hoses of your engine and come with standard pipe
thread connections in sizes ranging from 1/4" up to 1-1/2" with a cost
ranging from $93.30 up to $197.25 each. I would put one in either the water
pump supply or discharge line and a second one in the hose between the
engine and the exhaust manifold connection.
Where to look with in the engine are the two heat producing areas 1.) the
engine Block/Head and 2.) the exhaust manifold as mentioned in another
thread response.
Good Luck with this engine.
Jim


"Jeffrey P. Vasquez" wrote in
message ...
Hello all,

It's me again and I've a new riddle to pose to you. It's the S2 with the
raw-water cooled Yanmar in a marine environment again. Here's the latest:

1) Through-hull has been thoroughly cleaned.
2) Raw water strainer and hoses have been replaced.
3) Water pump has been replaced.
4) Thermostat has been replaced.
5) Mixing elbow has been replaced.
6) Entire system has been "Marsolved" (marine solvent)

Here are the symptoms:

When the engine is first started there is a good flow of water through
the system as evidenced from the exhaust. The engine runs to temperature
(150F) and operates fine indefinitely with no fluctuation in temperature
at operating rpm.

After operating at temperature for some fifteen minutes (arbitrary, but
approximately the time it takes to clear the marina and channel), the
engine is stopped and allowed to cool. After cooling the engine is
restarted and no flow of water is observed as evidenced by the exhaust.
Running at idle or at operating rpm does not alter the condition and the
engine heats to alarm. This has been confirmed in absence of sailing,
i.e. a siphon break was suspected (and may have been a past culprit), so
the hoses were rerouted to ensure positive pressure to the water pump
when the boat is level.

If the system is disassembled upstream to downstream (after cooling
sufficient to touch), flow through it at all points is observed. If the
system is reassembled it will at this point again function properly.

I would liken this behavior to vapor lock in automobile fuel systems, but
I have no understanding how this would be relevant to the Yanmar cooling
system.

The mechanic's diagnosis is blockage in the engine block itself and the
suggested recommendation is replace the entire engine.

Any opinions, experience, recommendations or wild-eyed guesses would be
infinitely appreciated as always. If engine replacement is the correct
course of action, what does one do with a Yanmar 2GM with about 1800
hours and a suspected cooling blockage?

Many thanks!

Did you replace the hose from the water pump to the Zinc Housing?

water flow from the water pump on my 15 arrives at the zinc housing in
a vertical orientation, I found as the zinc dissolves a crust would
build around the bottom inlet of the zinc housing at the housing/hose
junction restricting flow......










"Jeffrey P. Vasquez" wrote in message 6...
Hello all,

It's me again and I've a new riddle to pose to you. It's the S2 with the
raw-water cooled Yanmar in a marine environment again. Here's the latest:

1) Through-hull has been thoroughly cleaned.
2) Raw water strainer and hoses have been replaced.
3) Water pump has been replaced.
4) Thermostat has been replaced.
5) Mixing elbow has been replaced.
6) Entire system has been "Marsolved" (marine solvent)

Here are the symptoms:

When the engine is first started there is a good flow of water through
the system as evidenced from the exhaust. The engine runs to temperature
(150F) and operates fine indefinitely with no fluctuation in temperature
at operating rpm.

After operating at temperature for some fifteen minutes (arbitrary, but
approximately the time it takes to clear the marina and channel), the
engine is stopped and allowed to cool. After cooling the engine is
restarted and no flow of water is observed as evidenced by the exhaust.
Running at idle or at operating rpm does not alter the condition and the
engine heats to alarm. This has been confirmed in absence of sailing,
i.e. a siphon break was suspected (and may have been a past culprit), so
the hoses were rerouted to ensure positive pressure to the water pump
when the boat is level.

If the system is disassembled upstream to downstream (after cooling
sufficient to touch), flow through it at all points is observed. If the
system is reassembled it will at this point again function properly.

I would liken this behavior to vapor lock in automobile fuel systems, but
I have no understanding how this would be relevant to the Yanmar cooling
system.

The mechanic's diagnosis is blockage in the engine block itself and the
suggested recommendation is replace the entire engine.

Any opinions, experience, recommendations or wild-eyed guesses would be
infinitely appreciated as always. If engine replacement is the correct
course of action, what does one do with a Yanmar 2GM with about 1800
hours and a suspected cooling blockage?

Many thanks!

The older Yanmar seawater cooled (raw water) pumps were not very
efficient and could not maintain water flow in a warm engine if any
air bubbles entered the pump. After replacing the cam in the water
pump every 500 hours and the impeller every 100 hours at 6000 hours I
solved the problem by installing an air bleed tube ahead of the pump.
If water is present in the exhaust when running at the dock and it
stops after a while when running under power, then it is a good sign
that the combination of heat and exhaust pressure from the water lift
muffler are preventing the pump from passing small amounts of air.
These are a few of the things done in the ten years I tried to solve
the problem; Moved through hull lower in the keel. lowered the water
strainer below the water line, installed a forward facing scoop on the
through hull, Removed the cylinder head and dissembled the exhaust
heat exchanger, and installed a early warming horn set to sound at 145
degrees exit water temperature.

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

(Roy G. Biv) wrote in message . com...
Did you replace the hose from the water pump to the Zinc Housing?

water flow from the water pump on my 15 arrives at the zinc housing in
a vertical orientation, I found as the zinc dissolves a crust would
build around the bottom inlet of the zinc housing at the housing/hose
junction restricting flow......










"Jeffrey P. Vasquez" wrote in message 6...
Hello all,

It's me again and I've a new riddle to pose to you. It's the S2 with the
raw-water cooled Yanmar in a marine environment again. Here's the latest:

1) Through-hull has been thoroughly cleaned.
2) Raw water strainer and hoses have been replaced.
3) Water pump has been replaced.
4) Thermostat has been replaced.
5) Mixing elbow has been replaced.
6) Entire system has been "Marsolved" (marine solvent)

Here are the symptoms:

When the engine is first started there is a good flow of water through
the system as evidenced from the exhaust. The engine runs to temperature
(150F) and operates fine indefinitely with no fluctuation in temperature
at operating rpm.

After operating at temperature for some fifteen minutes (arbitrary, but
approximately the time it takes to clear the marina and channel), the
engine is stopped and allowed to cool. After cooling the engine is
restarted and no flow of water is observed as evidenced by the exhaust.
Running at idle or at operating rpm does not alter the condition and the
engine heats to alarm. This has been confirmed in absence of sailing,
i.e. a siphon break was suspected (and may have been a past culprit), so
the hoses were rerouted to ensure positive pressure to the water pump
when the boat is level.

If the system is disassembled upstream to downstream (after cooling
sufficient to touch), flow through it at all points is observed. If the
system is reassembled it will at this point again function properly.

I would liken this behavior to vapor lock in automobile fuel systems, but
I have no understanding how this would be relevant to the Yanmar cooling
system.

The mechanic's diagnosis is blockage in the engine block itself and the
suggested recommendation is replace the entire engine.

Any opinions, experience, recommendations or wild-eyed guesses would be
infinitely appreciated as always. If engine replacement is the correct
course of action, what does one do with a Yanmar 2GM with about 1800
hours and a suspected cooling blockage?

Many thanks!


I had this same problem on my 2GM on my 8.5M S2 and the problem was
corrosion build up. Here is what you do:

1. Ignore that idiot mechanic.

2. Get the engine service manual so you can trace the raw water
coolant path. It isn't obvious so get the manual. You could try
Mastry Marine in St. Petersburg, Fl to get it where I got mine.

3. Get a 5 gal bucket, get some clear nylon reinforced tubing from
Lowes or Home Depot the same size as your raw water intake tube. Get
a double hose barb to go into this and and join with your raw water
intake tube.

4. Close your raw water seacock.

5. Fill the bucket with fresh water and dump in a whole bunch of red
food coloring.. take the line off your raw water inlet and connect it
to the tubing.

6. Prime the system by pouring the red water into the clear tubing
and then hold your thumb over the end while you lower the end back
into the bucket of water.

7. Start the engine and using your thumb see if there is suction at
the end of the tube in the water. You can easily see if there are
bubbles or if the water is backflowing because you have used red
water.

8. Assuming you have suction indicating the raw water pump works,
disconnect the raw water pump outlet and observe the flow there.

9. Flow beyond the raw water pump only means the blockage is after
this point.

I forget how the raw water flows but it was not obvious to me without
the manual. I also forget exactly where I found the blockage but I
vaguely remember it was either where the water enters the heat
exchanger or the mixing elbow, cant remember. I do remember I had to
be looking toward the starboard side to see the blockage. Since my
engine access is from port side, I had to use a mirror. I used a
penknife, ice pick and internal battery terminal wire brush cleaner to
clear the blockage. No amount of solvent would have done the job.
Try to remove the chips.

I also vaguely remember being sorta aware of not getting water to
backflow so it enters the cylinder via the mixing elbow, not sure it
was really a concern.

10. After you find the blockage, rune several buckets of fresh water
throught he system before reconnecting the raw water.

11. When reconnecting the raw water, make sure you dont lose the
prime and make sure you have raw water flow.

BTW, you can also remove the innards of the heat exchanger and clean
them with stiff wire or replace them thus improving cooling.

GET THE MANUAL