Yanmar 2GM water cooling
 

Hi all

Some advice on where to look next would be greatly appreciated. I have
a Yanmar 2GM diesel engine that stops pumping water through the
cooling system after I have been out sailing for the day. To get it
started pumping again; I need to let the boat sit flat in the water
for about an hour. I have changed the impeller, but still have the
problem. The only time this seems to happen is when I have the boat
heeled over for a few hours.

Any ideas?

Thanks
Trai

Yanmar 2GM water cooling
 

Trai wrote:
Some advice on where to look next would be greatly appreciated. I have
a Yanmar 2GM diesel engine that stops pumping water through the
cooling system after I have been out sailing for the day. To get it
started pumping again; I need to let the boat sit flat in the water
for about an hour. I have changed the impeller, but still have the
problem. The only time this seems to happen is when I have the boat
heeled over for a few hours.

Trai, use Google to search rec.boats.cruising via the Groups section using
the keywords: yanmar overheating jeffrey. Read the thread (there are
several, but you're about at the point I was, so you can probably skip
everything I went through prior).

Apparently this is not a rare issue. Many insightful and helpful comments
and suggestions were posted by the many knowledgable people here.

Yanmar 2GM water cooling
 

Trai wrote:
Some advice on where to look next would be greatly appreciated. I have
a Yanmar 2GM diesel engine that stops pumping water through the
cooling system after I have been out sailing for the day. To get it
started pumping again; I need to let the boat sit flat in the water
for about an hour. I have changed the impeller, but still have the
problem. The only time this seems to happen is when I have the boat
heeled over for a few hours.

Btw, just out of curiosity, what is the boat and where is it located? The
boat discussed in the thread I referenced is a 1989 S2 (built on and for
the Great Lakes, afaik) that is now in San Francisco.

Yanmar 2GM water cooling
 

Btw, just out of curiosity, what is the boat and where is it located? The
boat discussed in the thread I referenced is a 1989 S2 (built on and for
the Great Lakes, afaik) that is now in San Francisco.

Hi there

Thanks for the reply - the boat in question is a Sunstar 28 and is
located in Vancouver BC.

I took a look at that thread and there is a lot of information there.
There are some differences in the problem however. The pump on this
boat will work any time, for as long as I want it to run, its only
after sailing (motor off) and the boat being heeled over for a long
period that it gives trouble. After about a hour of sitting at the
slip its all ready to go again. I am stumped :(

Yanmar 2GM water cooling
 

Yanmar 2GM water cooling
 

Marc Auslander wrote in
:

(Trai) writes:

The pump on this
boat will work any time, for as long as I want it to run, its only
after sailing (motor off) and the boat being heeled over for a long
period that it gives trouble. After about a hour of sitting at the
slip its all ready to go again. I am stumped :(

Sounds like the pump is loosing its prime. The pump is not good at
pumping air.

You might try priming it manually the next time it happens to see if
that fixes it. On my boat, I would do that by pulling the intake hose
off the thru-hull, poring water down it, then reattaching it.

I wanna look at his anti-siphon break in the exhaust hose and the position
of the hose's loop above the waterline when he's heeled over hard. When
he's heeled over, so is the loop. I agree the pump is coming unprimed, but
should prime again as soon as the boat goes upright. But, alas, if there
is water standing in the exhaust hose pushing back into the engine, the
bubble of air has no place to go out of the water pump impeller when it
starts turning. So, the engine is "vaporlocked" with that bubble of air
stuck in the pump. Normally, when the impeller starts to turn, the water
pressure from the seacock simply pushes the bubble out of the pump as the
impeller turns because the impeller is under the waterline so the bubble
moves on. If there is water in the exhaust pushing backwards on the
impeller, the air bubble in the pump is trapped and cannot let the impeller
prime. This will happen if the loop every gets so flat it allows water to
go over the loop to the engine side. Stand the loop back up and there's
now a water column trapped on the engine side of the loop. If there's no
leaks, the column is blocked by the stopped impeller acting as a valve.
(water doesn't flow by a good impeller in either direction unless it
turns). OF course, he COULD have a bigger problem if this is happening and
it shoves water in those exhaust ports into the cylinders. Been there,
recently, done that.....not pretty....

Larry