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Old 26-02-2013, 16:00   #1
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Join Date: Aug 2008
Location: San Rafael, CA
Boat: Banjer 37 motorsailer
Posts: 41
Perkins 4.236 Overheat

1972 engine, pushing around a 26000 pound boat.

How long should it take for this engine to get to operating temp? I've owned the boat for 5 years, finally began to use it frequently last year, two or three weekends a month, often overnighters. This engine has always taken almost 45 minutes to reach 180, the after i changed the coolant last year it stabilized at 190

Late latst year the engine suddenly made some odd noise then stoppend, we were in shoal water and dropped the hook. When the engine cooled, it started right up. and we nursed it the two miles home at low rpm. The rest of the year, maybe ten hours of motoring we ran with no problem.

Decided to take the heat exchanger apart for servicing, found some of the tubes plugged with SF Bay mud, but all was OK. Reassembled with new thermostat and gaskets and idled at dock, and new, entirely new water pump">raw water pump, it still took 45 minutes to warm up but everything seemed OK, as it had always been, No change in level of oil or coolant from when it was first fired up.

Four hours later, boat is packed for the first trip of the year and we head off, everything seemed fine until we put it up from idle in gear to 1300 rpm, then suddenly same noise and just as quick the engine stops, this time I notice the engine water temp is nearly pegged, way too hot, obviously. The next day I went back and found the water level in the Hx exactly where it was and the crankcase oil the same.

Raw water is flowing beter than ever with restrictions removed from the raw water system and new pump, new thermostat. The mystery is why does it take so long to warm up, and now why doesn't it cool. We are thinking maybe the engine water pump may not be pumping, after all it is 40 years old and could well be shot.

Thanks for your thoughts


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Old 26-02-2013, 16:10   #2
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Re: Perkins 4.236 Overheat

My 4.236 takes a good 20 minutes or so to get up to temp even if I am underway. I was having an overheating issue that turned out to be the thermostat gone bad. You may want to test the thermostat to make sure it is OK, even though it is a new one. Could be the freshwater pump isn't circulating, but usually you get leaking, wobble, some noise coming from it. Take off the belt and turn the water pump by hand and see how it feels. You may have some clogged passages in the block too.

Kettlewell Cruising
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Old 27-02-2013, 20:49   #3
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Re: Perkins 4.236 Overheat

I had a 4-154 that always overheated if run over 2000 rpm for any length of time. I just lived with it. What bothers me about your problem is that it ran OK for about 10 hours and then started overheating again. It is possible, but unlikely to have 2 thermostats go bad on you, so I think you need to look to something else. The first thing I would do is put a real loud overheat alarm so that you dont seize up your engine again. That can cause major damage. My 4-154 problem (the next owner told me) was that the cooling passages in the head were all rusted up, but the problem was consistent. Try running some kind of radiator cleaner thru the engine on the chance that it might clear up the problem. Very cheep to do , and if it doesnt work,,,OH WELL. ____Grant.
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Old 27-02-2013, 21:31   #4
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Join Date: May 2011
Location: PDX
Boat: Gulfstar 50
Posts: 1,031
Re: Perkins 4.236 Overheat

Let's see, my 4.236 takes 20 minutes plus to come up to temp. The gauge reads higher and higher and appears to go into overheat then the thermostat opens and the temp settles down to 185. I'm sure that I have a sticking thermostat that I should replace.

When I first got the boat the gauge read 230 plus and I thought that I had an overheating problem. I bought an IR temp guage online for about $30 and found out that it was actually at 185. This lead me to discover a fault in the gauge wiring.

You can fire it up with the expansion tank cap off and see if there is swirling (indicating coolant flow) in the tank. And also use the ir gauge (or your hand) to track the progress of heat through the coolant lines.

I am worried as to what the noise is. COuld it be a bit of localized boiling inthe coolant lines?

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