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  Overheat Alarm at high rpm?

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Author Topic:   Overheat Alarm at high rpm?
george nagy posted 05-28-2002 12:36 PM ET (US)   Profile for george nagy   Send Email to george nagy  
Is it possible that the engines position on the ransom and trim position could cause an overheat alarm to sound?
1997 johnson ocean runner mounted 1 hole up with fast track. otherwise ran well at 3,000 rpm and under.
Tom W Clark posted 05-28-2002 12:44 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

Are you sure it was an overheat alarm and not a fuel restriction alarm? Do you have a temp gauge to confirm?

george nagy posted 05-28-2002 01:02 PM ET (US)     Profile for george nagy  Send Email to george nagy     
I have the system check guage and it said hot. I could hold my fingers on the block for only a few seconds.
scattcat posted 05-28-2002 01:29 PM ET (US)     Profile for scattcat  Send Email to scattcat     
I had a similar problem with a 1989 110 Johnson It would be fine at mid range and below but would overheat at WOT, My first thought was sticky thermostats restricting water flow but it turned out to be a weak water pump that could not provide adequate flow of water to cool the engine at WOT. replaced water pump and problem was solved...
peteinsf posted 05-28-2002 05:49 PM ET (US)     Profile for peteinsf    
It also could be a blown head gasket. The fuel gases will blow into the water jacket and cause over heating at higher RPMs.
george nagy posted 05-28-2002 06:49 PM ET (US)     Profile for george nagy  Send Email to george nagy     
Wouldn't a blown head gasket show up in acompression test or even show signs of water in the spark chamber. The compression is right on the money on all cylanders and the plugs look fine. I was thinking of trying to get some melt sticks and change the impeller. I removed the thermostats, cleaned them, flushed the engine, and took off the lower unit to inspect the water pump. The impeller doesn't look that bad to me. I was also thinking along the lines of some slightly off timing settings which could cause some sort of heat buildup. I'm thinking more along the lines of water supply because the engine seemed to run great otherwise.
acseatsri posted 05-28-2002 07:30 PM ET (US)     Profile for acseatsri  Send Email to acseatsri     
If you took the time to remove and inspect the impeller, it would be advisable to just replace it. it's NOT that expensive, and it doesn't take that much deformation or wear to weaken it enough so as to contribute to overheating. VERY cheap insurance.
george nagy posted 06-03-2002 10:23 AM ET (US)     Profile for george nagy  Send Email to george nagy     
It was the impeller! Put on a new one and away I went engine runs great and I love my boat again!

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