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Engine running a bit hot


robbio c
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Good morning all .I have a Mitsubishi s4l2 keel cooled engine on my boat .It was installed by a Dutch company and they said it should run at between 80-85c .I've only been out on it a few times and it's running at just under 90c but remaining stable at this temperature .There is plenty of coolant and belt tension for pump is fine and the prop I don't think it is fouled I have no weed hatch so can't visually check but it doesn't deemed restricted .There is no calorifier in the cicuit yet.It does need a blacking and was wondering bottom been dirty might hinder cooling efficiency. Any thoughts appreciated. I've been cruising at 1500rpm .Rob

Edited by robbio c
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1 hour ago, robbio c said:

It does need a blacking and was wondering bottom been dirty might hinder cooling efficiency.

 

While I agree you don't need to be worried about it, it's definitely worth giving the outside of the skin tank a good scrape back to steel before blacking it again. 

 

There a quite a few boats that overheat because they have half an inch of bitumen blacking on the outside of the skin tank, and they usually only find this out when needing to push hard on a river...

  • Greenie 2
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90 degrees should be ok and as others have said the gauge cannot be totally relied on. On my barge there was a GM 110hp engine which was keel cooled by an external pipe and it always showed 85  but when it was changed for a new Perkins Sabre 

130hp engine the new supplied instrument panel  showed a little over 90 all the time. At the next docking I had the external pipe length increased and it still showed the same. The volt meter in the panal used to show over 30 volts quite often and when I contacted Sabre I was told to tap it and it went back to 28 which was right, so these instruments cannot be relied on.

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Just now, robbio c said:

Thanks guys  mine is also cooled with two external pipes underneath boat not a skin tank on the side.Rob

OK, but the same applies to the pipes as to a skin tank - if it's too thick with blacking, clean it off before re-blacking.

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I think the important point is whether the temperature is under the control of the thermostat, or not. If it gets to 90 at 1500 and is still at 90 after a while at 1800 or whatever, then the thermostat is doing its job and all is fine. If it goes over 90 when you run the engine faster than 1500 then the thermostat is already wide open and there is a lack of adequate cooling.

 

As others have said, also corroborate the gauge reading with another thermometer. If it really is at 90C and you have a calorifier then the hot water coming out of the tap is going to be at 90c which is a bit dangerous. If so, I’d try to get a cooler thermostat ie around 80C

Edited by nicknorman
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1 minute ago, Stilllearning said:

It may also be worth considering a flush out of the skin tank, in case there is a build up of sludge in the bottom of the tank, thus rendering it less efficient.

No skin tank!

 

However if there is a lack of adequate cooling, a buildup of scale etc inside the cooling pipes is one explanation.

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15 minutes ago, nicknorman said:

I think the important point is whether the temperature is under the control of the thermostat, or not. If it gets to 90 at 1500 and is still at 90 after a while at 1800 or whatever, then the thermostat is doing its job and all is fine. If it goes over 90 when you run the engine faster than 1500 then the thermostat is already wide open and there is a lack of adequate cooling.

 

As others have said, also corroborate the gauge reading with another thermometer. If it really is at 90C and you have a calorifier then the hot water coming out of the tap is going to be at 90c which is a bit dangerous. If so, I’d try to get a cooler thermostat ie around 80C

Depends on whether there is a blending valve on the calorifier to limit the water temperature to the taps. If there is, you don't have a problem!

Richard

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52 minutes ago, nicknorman said:

If it really is at 90C and you have a calorifier then the hot water coming out of the tap is going to be at 90c which is a bit dangerous. If so, I’d try to get a cooler thermostat ie around 80C

Or a TMV on the outlet of the calorifier,

 

MP.

 

ETA pre-empted by OP.

 

Edited by MoominPapa
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