Interesting, Trevor. I don't think that is where my overflow is coming from, since it happens when M not heating water except by the Yanmar. There is no contamination of the hot water either. Wouldn't you think that the superheated coolant flowing thru the water heater coil would make its way into the hot fresh water? Also, the water in the overflow tank is dirty, which I think has to come from the sea water side of the exchanger.

Now I wish I'd tasted the water I just drained out of the engine. There wasn't a trace of green antifreeze color, so essentially all of the coolant had been replaced with sea water. If I'd tasted it I'm sure it would've been salty. If it had not, your explanation would explain it.

Anyway, I've drained the coolant side and added antifreeze so hopefully the engine will be protected while I get a new heat exchanger.

Thanks again,
Kent
SM243 Kristy
Brunswick GA USA

Sent from my iPhone

On Sep 2, 2013, at 5:13 PM, "seafeverofcuan" <seafeverofcuan@...> wrote:

Kent,
I am not sure that I have all the components of this thread so forgive me if I have missed something.
One certain way that the overflow bottle on the Yanmar will overflow is if you have a failed coil inside your calorifer.
If you are making hot water using the electrical element either by shore power or the generator once the fresh water inside the tank heats up it will expand and should there be a pin hole leak in the second element that is plumbed to the engine, the fresh water will expand creating enough pressure to force the engine coolant water back through the Yanmar block and up and out of the bottle.
Why it would be happening with the Onan is a bigger mystery unless it also has it's freshwater engine coolant plumbed in a circuit through the calorifer as well?
Regards,
Trevor

Seafever
SM 425
Mexico

--- In amelyachtowners@..., <karkauai@> wrote:

I have just discovered that the overflow tank for both the Yamar and the Onan is overflowing. The water is dirty. I'm guessing that the heat exchanger for the Onan is leaking salt water into the coolant. Both engines run fine, and the Yanmar only has ~100 hours on it.
Anything else that could cause my problem? How big a job is it to replace the heat exchanger?
Thanks
Kent
SM243 Kristy
Brunswick GA USA

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