Overheat alrm on 89, 90 hp

[pagraham]

The overheat alarm sounded today while I was out, at first I could keep my hand on the head and flywheel for 3 seconds, then it seemed to get hotter. After a while it just quit sounding, pulled wake board for a while without incident, what should I be checking, had good pee stream and motor is a fresh rebuild for Shaver St. Marine, thanks

 

[emdsapmgr]

Re: Overheat alrm on 89, 90 hp

It would be unusual for an overheat on a fresh engine. Usually the overhauler will install a new impeller, thermostats and water diverters as a result of the overhaul. You may have run over something, like a plastic bag-which temporarily covered the water intakes. If the thermostats were not replaced, you might want to consider that. You can have an overheat at idle with strong telltale if one of the two thermostats is stuck shut. A stuck stat won't let the hot water out of that side of the block at idle. Once on plane, the pressure relief valves open, flooding the block with extra cooling water.

 

[pagraham]

Re: Overheat alrm on 89, 90 hp

I pulled the T stats, everythings looks good and clean, I will go ahead and install a new t stat kit. I purchase the factory service manual, I don't see water diverters, where would I find these? thanks

 

[DJ]

Re: Overheat alrm on 89, 90 hp

The divertors are under the head covers (water jacket). THe manual clearly points them out.

If they are missing, you will get "hot spots".

 

[pagraham]

Re: Overheat alrm on 89, 90 hp

Took the boat for a ride today and again the overheat alarm sounded after about a quarter mile run on plane from the ramp. When I got out to the channel I throttled back and thats when I heard the alarm, damn thing is hanging inside the console, I should mount it thru the console face because I don' hear it unless I slow way down. Turned it around and headed back, as we crused along at no wake speed the alarm cuts out intermitant and then it shuts off. Both times it has gone off was after a few minutes on plane at around mid range. Back at home, on the flusher, it won't overheat. Put it in a barrel and it would not overheat. I bought an lazer thermometer gun and forgot to take in the boat today, but in the driveway the heads are around 145 degrees on a hose and in a barrel. Seems to only alarm after it has been under load for a bit. Lookin for advice, thanks

 

[Sixmark]

Re: Overheat alrm on 89, 90 hp

If this is a fresh rebuild then I would recommend taking it back to them and having them look at it before you get too in depth, once you go so far with taking things apart or replacing things then you may void whatever warranty you may have on the rebuild.

 

[boobie]

Re: Overheat alrm on 89, 90 hp

The water deflectors are under the cyl head and in the block itself. Not in the cyl head water cover passages.

 

[emdsapmgr]

Re: Overheat alrm on 89, 90 hp

145 is normal on the hose when idling. The stats must be working if both heads warm up to that temp. When the boat planes out, the pressure relief valves open in the thermostat housing, flooding the powerhead with extra water. Possible you have a problem with these nylon valves. Would be interesting to put a 0-30 lbs pressure gauge on the telltale hose fitting. See what the pressure is when you are on plane. Should be around 18-20 lbs. Sixmark is right on about contacting the rebuilder. That's the person that will determine any warranty on the powerhead.

 

[Hayraker]

Re: Overheat alrm on 89, 90 hp

Check to see if your alarm is grounding itself out under the dash. I had just about the same thing with my 90, 70 hp.