Heat exchanger

[Bill O'Donovan]

I was thinking of replacing the thermostat on my 18 Yanmar 2GMF as a precaution at 250 hours, but my engine guru suggested instead that the heat exchanger is the Achilles Heel of the Yanmar diesel.He warned that that mix of seawater and fresh water can corrode and compromise the coils of the exchanger. Once one of the coils fails, disaster will result with the coolant suddenly sucked out of the enginer along with the seawater. He suggested removing the exchanger for pressure testing by a radiator shop. I looked at the drawings, looked at the engine, and I remain clueless where to start to dismantle the thing.So I'm curious: Has anyone experienced such failure? Any advice?

 

[Steve Dion]

Waste of time and money!

Bill:250 hours on one of these engines is like brand new. I follow this up with asking you how old it is. These engines are good for 10,000-15,000 hours. I must presume that your boat gets pulled every year or every other year and winterized each year. This actually is flushing out your raw water system. What happens is the heat exchanger will get plugged up from the seawater and the mixing elbow also cokes up.Do not get me wrong, there is nothing wrong with maintenance but you really do not need to get parinoid about it. PS: are you have any problems now?

 

[Tim Leighton]

CONCUR

Bill: Steve is correct. When my 31 (with a 2GMF - 15hp) was only a few years old I had an almost vertical learning curve when she started overheating. One of the things I did to troubleshoot (stupidly, unnecessarily) was to dismantle and clean the heat exchanger thinking it may be clogged. Wasn't all that hard, but a messy, long job. Absolutely nothing wrong with the exchanger tubes (approx 300 hrs on engine at time). Since then, I've taken the end plates off a few times and inspected using a flashlight and have never seen any buildup. I would respectfully suggest your "engine guru" is incorrect. As Steve says, winterizing the engine should take care of any buildup in the exchanger. For whatever it's worth, the mixing elbow and SW nipple on it from the exchanger are far more likely to coke up and cause overheating than the exchanger itself. The mixing elbow isn't any fun to remove/clean either, but would be a much better use of your time/money. That job is on my periodic maintenance schedule and done every 2 years. Good luck!Tim Leighton

 

[Jim Oursler]

On my 3GMF heat exchanger covers are 2, help on each by 4 nuts. At one end is a water inlet, at other is the exhaust water. Once cover removed on forward end of engine, you pull it. Definitely easier if you remove both covers, so you can push it. I highly recommend a Yanmar engine repair manual.. or take a look at the manual at a local Yanmar engine repair shop. Anymore hellp..you can call me at 469 235 1279 . I am not a mechanic.but have chased around the water system a lot.