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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel
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  #11  
Old 07-13-2013
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Re: Yanmar 2QM15: strange overheating incident

I had a raw water cooled Volvo in a boat we owned a number of years ago. The thermostat is in the salt. It got funky like you describe and was very easy to replace. Do it yourself job....cannot hurt to try it.
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Old 07-14-2013
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Re: Yanmar 2QM15: strange overheating incident

That's my next step.
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Old 07-16-2013
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Re: Yanmar 2QM15: strange overheating incident

I haven't pulled the thermostat yet, but have some new symptoms to post, for the sake of anyone who may read this thread in the future.

Took the boat out for the afternoon, and ran the engine for a couple hours. Like the last time, the temperature was stable, but about 10 degrees higher than normal (running about 135F, vice 125F).

I pulled the raw water strainer basket, and it looked clean at first glance, but when I looked closer, there was what appeared to be a small jellyfish in the bottom. But I think what it really was was an accumulation of bio-slime. I scrubbed out the basket thoroughly and replaced it. After starting engine again, temps seemed to drop a bit, but time was running short, and I wasn't able to perform a thorough test.

I'm still planning to pull, and perhaps replace the thermostat as part of an upcoming maintenance evolution.
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  #14  
Old 07-16-2013
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Re: Yanmar 2QM15: strange overheating incident

There's no rule that says it has to be one thing. Maybe a weak thermostat AND a slightly clogged intake AND a missing impeller blade...
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Old 08-04-2013
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Re: Yanmar 2QM15: strange overheating incident

I haven't had an opportunity to pull the t-stat or head yet, but I went out for a few hours this afternoon (first time in a couple weeks). I kept a close eye on the temperature, and as soon as it started to creep up (which took about 45 minutes), I throttled down and was able to maintain temps that way. But I also noticed that I've lost about a knot off hull speed, and the engine seems to be working harder than usual. I also noticed some black smoke at full throttle, which I haven't noticed before.

Suspecting bottom growth, I called a local diver when I got home. He had just cleaned my boat in early May, and the paint was in good shape, so he doesn't think that excessive bottom growth is the problem. But he does strongly suspect that barnacles on my prop are the culprit, since my prop is unpainted, and boats in my marina experience heavy barnacle growth in May/June (he lives aboard in the same marina). Cleaning is scheduled for later this week.

So back to the original post: might barnacle growth on my prop be contributing to my mild overheating condition?
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Old 08-08-2013
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Re: Yanmar 2QM15: strange overheating incident

..and your results?
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Old 08-08-2013
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Re: Yanmar 2QM15: strange overheating incident

Quote:
Originally Posted by Rusty123 View Post
I haven't had an opportunity to pull the t-stat or head yet, but I went out for a few hours this afternoon (first time in a couple weeks).
Okay i gotta get this out there- you have an engine that is becoming increasingly unreliable, repeatedly overheating, and instead of taking fifteen minutes to pull the thermostat and fix the problem, or at least knock one suspect off the troubleshooting list, you went sailing?
The problem is not going to get cheaper to fix, the longer you ignore it. Even running slower as an overheating workaround is not doing the engine any favours.
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Re: Yanmar 2QM15: strange overheating incident

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Originally Posted by aa3jy View Post
..and your results?
Parts came in, so I swapped out the T-stat and impeller. Also topped off oil. Hull and prop was cleaned a couple days ago.

Took her out for a spin, and everything seems normal. Temps are good, speed was good, engine rpm back to normal.

Not sure which (or all) of these was the main contributor, but problem seems to be resolved.

Thermostat was rust stained and spattered with small particles of gunk, but no major obstruction. I ordered a gallon of rydlyme for a flush though.

Thanks for the suggestions.
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Old 08-29-2013
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Re: Yanmar 2QM15: strange overheating incident

I pulled the mixing elbow - it's surprisingly plugged up. But the exhaust manifold looks good. I've read that this can contribute to overheating (as well as other symptoms), so I'm hopeful that the new elbow will help.
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Old 09-09-2013
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Re: Yanmar 2QM15: strange overheating incident

Rydlyme flush: check
New thermostat: check
New exhaust elbow: check
New exhaust hose: check
New raw water discharge hose: check
New raw water impeller: check

Result: 5 hour run at 80% max RPM, cool as a cucumber.
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