engine overheat guidance

[Redbeard33]

unfortunately it might not be an quick easy fix, i have the same boat with the same engine and had the same issue, it turned out that the interior coolant passages were extremely scaled (raw water cooled engine), descaling flushes wouldn't solve the problem and I had to pull the engine and strip it down on a stand. the coolant passages in the head are fairly accessible once its removed but the passages in the block itself are narrow and deep i had to resort to a wire coat hanger to chip it all out. compressed air is the best way to clear the loose junk. the good news is its not a hard job if you dont mind taking on a project and putting the boat out of commission while you have the engine out

 

[rardiH36]

unfortunately it might not be an quick easy fix, i have the same boat with the same engine and had the same issue, it turned out that the interior coolant passages were extremely scaled (raw water cooled engine), descaling flushes wouldn't solve the problem and I had to pull the engine and strip it down on a stand. the coolant passages in the head are fairly accessible once its removed but the passages in the block itself are narrow and deep i had to resort to a wire coat hanger to chip it all out. compressed air is the best way to clear the loose junk. the good news is its not a hard job if you dont mind taking on a project and putting the boat out of commission while As you have the engine out

Glad to see your report of successfully cleaning out the scale build-up inside the engine. I had thought that once this occurred, the engine was pretty much done for.

As I have observed before on this SBO Cherubini forum .... Amazing the variation of Yanmar setups that Hunter used during their Cherubini era. Just a conjecture that Yanmar must have been offering a pretty good price to Hunter for the raw water cooled versions. Perhaps this might have been during the period when the industry was trending towards self contained fresh water (anti-freeze) cooling. For many of the 36 and 37 Cherubini's, Hunter opted to install the raw water cooled Yanmar enegines, but then Hunter "upgraded" them into to self contained anti-freeze systems by Hunter's own modification with the addition of an externally mounted heat exchanger. Saved then engine from seawater coursing through it. But us owners are stuck with the lower 125-140F thermostat. Some engine efficiency is lost. And the lower engine temp not too good for making hot water in the shower.

 

[Stephen Trapani]

Glad to see your report of successfully cleaning out the scale build-up inside the engine. I had thought that once this occurred, the engine was pretty much done for.

As I have observed before on this SBO Cherubini forum .... Amazing the variation of Yanmar setups that Hunter used during their Cherubini era. Just a conjecture that Yanmar must have been offering a pretty good price to Hunter for the raw water cooled versions. Perhaps this might have been during the period when the industry was trending towards self contained fresh water (anti-freeze) cooling. For many of the 36 and 37 Cherubini's, Hunter opted to install the raw water cooled Yanmar enegines, but then Hunter "upgraded" them into to self contained anti-freeze systems by Hunter's own modification with the addition of an externally mounted heat exchanger. Saved then engine from seawater coursing through it. But us owners are stuck with the lower 125-140F thermostat. Some engine efficiency is lost. And the lower engine temp not too good for making hot water in the shower.

Yeah, but the thing lasts forever. My raw water cooled 36yo 2qm15 has virtually no visible wear in the cooling passageways or in the combustion chambers. Entire life in salt water. Astounding really.

 

[qazvick]

Well.... finally got to it... I wish I would have realized there was a thermostat on this engine as it ended up being the culprit. My uneducated assumption was that it just flowed sea water through the engine, unchecked.

Never the less, she's back to running great! I really appreciate all the responses.

 

[Nelsonhow]

Did you get the problem resolved?
What was it?

 

[qazvick]

Yes. Rusty thermostat.