Yanmar 2QM15 Overheating Problem - Page 2 - SailNet Community
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post #11 of 19 Old 09-02-2011
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I wouldn't use RTV. The gaskets will do the job well unless you have eroded sealing surfaces. Looks like you have all the gaskets listed. Don't you need two zincs (fore and aft)? Zinc packing is copper washer, and usually reusable, but they're inexpensive so I would replace both. Soot in the manifold and exhaust elbow are not a problem, unless it is a very thick coating. It will build back up quickly. You need to run up the engine each time you run it, especially before shutdown for a minute or two, to blow any soot out.

If you were able to dig out and flush out the manifold well, and water is flowing freely through it while it is off the engine, you probably have solved your problem.
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post #12 of 19 Old 09-02-2011
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Agree about not using RTV. Permatex makes several products for coating gaskets to improve sealing. Check your local auto parts store.
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post #13 of 19 Old 06-11-2013
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Re: Yanmar 2QM15 Overheating Problem

This has been a great thread. I recently bought a 1966
Columbia 29 Mark2 with a converted 2QM15 with purported flow problems. The boat had been neglected for three years and the forward zinc was down 50% and its debris had occluded the bypass tube. I scraped all of that out. The aft zinc was totally gone. Problem? Engine won't warm up. I bought and installed a mechanical temp gauge that begins at 130F and it won't come off the needle. I'm going to replace with one that starts at a 100F. The thermostat looks OK but I haven't tested it on the stove yet. Why is there a 5/32" hole in the top end? Any ideas why it might not be warming up? Current sea temperatures are about 53F. What temp should the thermostat open at and what is the usual operating temp? The manual says not enough to burn your fingers.
Thanks for any help. Hope I am not cutting in on someone's thread.
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post #14 of 19 Old 06-11-2013
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Re: Yanmar 2QM15 Overheating Problem

I believe the normal operating temperature is about 130. That was about as hot as mine ever got and that was in 80 degree water. Rule of thumb I was taught was that you should be able to put your hands on the block for a few seconds without getting burned. It should be very warm but not "burning hot".
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post #15 of 19 Old 06-12-2013
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Re: Yanmar 2QM15 Overheating Problem

The 2QM15 thermostat begins to open at 42C (108F) and is full open at 52C (126F). That's why your thermometer doesn't register. The hole is likely an equalization hole to limit pressure/temp differences when the thermostat is closed during warmup. Sounds like your engine is being adequately cooled. Your goal of clean water passages and zinc protection and good cooling seem to have been met. Bravo!
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post #16 of 19 Old 06-12-2013
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Re: Yanmar 2QM15 Overheating Problem

Thanks to both of you for your helpful replies. I stove tested my thermostat this evening and it seemed like it was opening at about 100F. I'm a car nut and it just seemed to me that 85F was low for a healthy operating temp but maybe it's good. Does Yanmar offer higher temp thermostats? Should I look for one with a higher temp rating? BTW, is Slick 50 a good idea in a diesel?
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post #17 of 19 Old 06-12-2013
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Re: Yanmar 2QM15 Overheating Problem

Contact Torresen Marine to find out about the thermostat. I wouldn't use Slick 50. Don't know if it would hurt anything but...why?
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post #18 of 19 Old 06-13-2013
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Re: Yanmar 2QM15 Overheating Problem

The reason for keeping the water temp low in a raw-water cooled engine is to minimize scaling in the engine cooling passages. The Universal 5411 in my previous boat ran at about 140F. Fresh-water cooled engines run the cooling water (anti-freeze) at 180F.
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post #19 of 19 Old 06-18-2013
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Re: Yanmar 2QM15 Overheating Problem

Thanks everyone for the input. I won't slick 50 it. I probably should have titled this "Underheating Problem". More and more I am thinking that this is not a problem. Engine is currently running at about 85-90F and maybe that is what I should suspect at low load, low rpms in 52F water. I'll move on to my next major problem- trying to find a new/used lower gudgeon for my Columbia 29 MarkII. or some pictures/specs, material. Mine is gone, probably a victim of galvanized corrosion. Last owners spent most of their time destroying the original interior.
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2qm15 , diesel , overheating , raw water , yanmar

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