Overheat alarm on 1988 40 hp evinrude

[byfscbn]

Hi, My overheat alarm is going off in the helm control. here is what I have done so far: Replaced the thermostat, and gasket, made sure the pressure relief valve was not sticking. Replaced water pump impeller. When I hook it up to the earmuffs it picks up and pumps a strong stream and never seems to get warm ( the water out of the pee tube) the heads do get hot enough that you cannot keep your hand on it for long. I am at wits end , what do i do next. The motor has very low hours and has been sitting for the past 5 years.

 

[EN2]

Re: Overheat alarm on 1988 40 hp evinrude

The water out of the tell tale will never be warm, water pressure is before the power head. You might want to check compression and look at the plugs if one looks steam cleaned, check for a blown head gasket.

 

[byfscbn]

Re: Overheat alarm on 1988 40 hp evinrude

Thanks,

I checked the compression, and the bottom cylinder is at 150 psi and top at 130. Does this indicate a blown head gasket? Thanks again for your help, this motor was his grandfather's and he really wants to use it.

 

[EN2]

Re: Overheat alarm on 1988 40 hp evinrude

What do the sparkplugs look like?

 

[byfscbn]

Re: Overheat alarm on 1988 40 hp evinrude

The plugs look normal, a little oily, I checked the compression and it is now 150 each cylinder, 10 psi leakdown in 12 seconds each, took it to the lake and it idles great, accelerates great but the overheat alarm is still going off. The exhaust stack seems to be getting too warm. Is there some kind of blockage in the head I am not thinking about. Thanks for your patience with this matter.

 

[EN2]

Re: Overheat alarm on 1988 40 hp evinrude

Take a look at the water intake screen on lower unit, four holes on each side. Make sure these are not clogged. Sometimes during long lay up bugs and such critters like to use these for homes.Shine a flashlight through from one side while looking at the other.You mentioned replacing the impellor. what condition was the impellor cup and wear plate in? P.S. There is a thick rubber ring that fits on the top of the water pump housing,drive shaft goes through it, make sure this is in place.