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Old 02-08-2012, 13:27   #1
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hot diesel

my morgan 33 was repowered in 08 with a phasor/kubota engine. i bought boat oct 10. engine ran fine on 400 mi run in feb 10. very limited usage since. for at least 18 months engine has been running hot if i take RPMs over 1800 for 15 minutes or so (190 rising). back off revs to 15-1600 and temp drops and stabilizes at 175. local mechanic with good rep tried-remove/clean cooling system,check impellers, thermostat, clean sea water intake, recondition water pump, etc. no change. temp gauge is accurate. scraped bottom with no change. i did pick up a line on the prop on the trip dawn but no real problem removing so i do not think that is it . hopefully someone will think of something we haven't tried .
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Old 02-08-2012, 13:47   #2
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Re: hot diesel

Does your engine rev to rated rpm underway. That will tell you if you have something binding that is eating up hp and causing the overheat. This is almost always accompanied by black smoke.

If you can find a spec for the raw water pump, check the flow rate. Place a 5 gallon bucket under the exhaust and time how long it takes to fill.

A couple of things that you haven't checked that could lead to low RW flow: collapsed intake hose and plugged exhaust elbow. Yanmars are notorious for the latter but don't know about Phasors.

If the flow is ok then I would suspect a fouled RW heat exchanger. Remove heat exhanger and pull end caps and run a rifle brush of the right size down the tubes to clean out the majority of the junk. Then fill with 50/50 Rydlime or CLR solution and let set for a few hours. Rinse and reassemble.

David
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Old 02-08-2012, 14:08   #3
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Re: hot diesel

If you haven't checked it, be sure the intake hasn't had someone crawl in and make it home. Pull the hose off the intake sea cock and run a rod down it.

What's the temp setting of the thermostat?? Assume it's 175 but if it's higher, 190 degrees could be normal. FWIW, 190 degrees isn't really hot. With a pressurized cooling system temps over 210 degrees aren't all that suspect.
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Old 02-08-2012, 21:00   #4
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Re: hot diesel

I assume from the temps you are talking about, that you have a fresh water cooled engine with a heat exchanger. My last boat had a Perkins 4-154 that when I purchased it had a faulty rubber end on the heat exchanger, that allowed salt water to circulate into the engine block. It took me a couple of monthes to recognize the problem and then I replaced the end fittings on the exchanger and that solved the problem(sort of). Even after fixing the problem the engine would overheat if run above 1800rpm for any length of time. This did not bother me as I was used to small engines or no engine at all. I ran the Perkins for 8 years like that and after selling the boat the next owner removed the cylinder head and discovered that all of the cooling passages in the head were completly clogged with rust. This was from salt water getting over into the fresh water side of the system before I owned it. Your engine may have salt water getting into the fresh water side and creating rust or just growing critters that would never grow in antifreeze. Also look to see if the raw water impellor has shed some blades that are blocking the exchanger intake. A much more common problem than is talked about. With all of the advice on this thread you will solve your problem.____Grant.
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Old 02-08-2012, 21:23   #5
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Re: hot diesel

If it isn't boiling over i.e. lifting the relief on the rad cap, chances are it's not over heating.
As was mentioned earlier the temperature sounds about normal for closed cooling system.
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Old 03-08-2012, 09:26   #6
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Re: hot diesel

In re-reading your post, it seems that your mechanic checked all of the right things, but the 175 degree temp seems rather low for a diesel. Most freshwater cooled diesels run at the 190 to 200 range. The higher temps give better combustion and supposed to give longer engine life. Check the owners manual to see what it is designed to run at. Also , you could have an erratic temp guage and not actually have an overheating problem at all. You might hit the auto parts store and put a mechanical guage on for a test. Good Luck with it, and let us know what the solution turns out to be?______Grant.
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Old 03-08-2012, 09:38   #7
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Re: hot diesel

Our Phasor Kubota does the same thing.......it's not overheating, the heat exchangers are a tad too small on some of the engines so the thermostat used is around 170F.
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Old 03-08-2012, 10:36   #8
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Re: hot diesel

at what revs does your phasor start to run over 180 degrees? if you back the revs down to that level does the temp start to drop in a few minutes?
is the thermostat located at the radiator cap similar to a car?
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