Yanmar 3YM30 overheating - finale

[Scott B]

As a follow up to my previous post http://archives.sailboatowners.com/pviewarch.htm?fno=0&sku=2008018083427.82&id=514132&ptl=Hunter Yanmar US have now agreed to replace my heat exchanger. I wanted to keep the previous post alive to finally close it off one way or another but let it archive. I wanted to post this for the record and for anyone else having this problem and searching the archives. There is another boat that I know is having the overheating problem and waiting to hear back from InMar ( Total Power). I think this will resurface from time to time as the boats get older and used more.Its amazing the power of the internet. Many years ago, I could not have resolved this without the help of the various forums and mainly this site.

 

[sailaway78]

Yanmar heat exchanger

I don't remember seeing this post before, or I would have made a comment. I have a friend who bought a new Hunter, fresh water cooled Yanmar. This thing would get hot any time it was running over 15-1800 RPM. After many so called fixes, a lot of trial and tribulation, it was finally discovered that the heat exchanger had been shipped from the mfg. with a cosmoline coating onside it. The cosmoline had not been removed, and as a result the heat exchanger could not do it's job as it should. Removal of the cosmoline fixed the problem.

 

[sailaway78]

Should have said

Had my fingers engaged with my brain not. Should have read cosmoline inside it, not outside.

 

[Scott B]

Cosmoline theory

I read many earlier posts that had the cosmoline theory either not being cleaned out by Hunter/Jenneau/???? or the dealers. Other theory was using 100% antifreeze and under use would cook the anti-freeze and coat the heat exchanger. Eventually Yanmar changed the exchanger to a larger unit in production and offered to clean and / or replace the exchanger on the older engines, but only if the owner experienced overheating. The Marine Service Advisory issued by Yanmar was kept relatively quiet and was only issued to distributors.

 

[Joseph Shirley]

Yanmar overheating

I was not aware of your earlier post but find it interesting. The 3YM30 is not the only engine with the problem. I have had a similar problem with my 3HM35(F) which is no longer manufactured. I can run at 2850 all day without a problem but overheat at 2900+ in about 10 minutes. I have changed impellers, Boiled out and rodded out the Heat Exchanger, changed the fresh water pump, changed: Mixing elbow twice, thermostat, entire exhaust system. raised the exhaust exit to reduce back pressure, and reduced my prop pitch to increase salt water volume and reduce the load, and I still have problems. I an ready to pull my exhaust manifold to check my exhaust valves for carbon. I haven't tried the entire engine cleanout so maybe I'll try that. Yanmar has been of no help at all.Actually I do 6.25 kts at 2850, so I continue to use the boat but I sure would like to get it fixed.

 

[Jim Rushing]

Have a friend

that had a Yanmar overheating problem with his new at that time C387. Catalina and Yanmar went round and round trying to find out what the problem was. It would run just fine until you pushed the engine a little. Then it would overheat. He went thru the prop changeout phase,the impeller changeout phase, and the heat exchanger checking phase. Finaly, someone noticed that the cooling water hoses on the engine/boat were not connected right. Came from the factory that way. When they replumbed the engine the correct way, the heat problem went away.