1996 90HP HOT light comes on

[pilot10010]

I have a 1996 Johnson 90HP on a 1968 Nauset Boston Whaler I just bought. The engine had not been run for a little over a year. It started great but the HOT light kept on coming on. It has a new water pump and there is pee water coming through the back. It accelerated nicely and seems to have lots of power. The pee water is warm to occasionally hot but not hot enough that you can't keep your hand on it. I don't get it... It's driving me crazy!!!

 

[wilde1j]

Re: 1996 90HP HOT light comes on

You need to determine if it's really overheating. Can you put your fingers on the cylinder head w/o getting burned when the light comes on? If you can, it's not overheating. Then look for a bad temp sensor, wiring issue, etc.

 

[tashasdaddy]

Re: 1996 90HP HOT light comes on

also could be tstat.

 

[pilot10010]

Re: 1996 90HP HOT light comes on

I am away right now so I cannot test that right now. If the engine was overheating wouldn't the pee water be boiling or at least really really hot to the touch?

 

[tashasdaddy]

Re: 1996 90HP HOT light comes on

the tale tell stream, has nothing to do with the temperature. it is only and indicator that the water pump is working. it is not an indicator that the tstat is opening allowing water to circulate thru the block.

 

[pilot10010]

Re: 1996 90HP HOT light comes on

Thanks for the reply. I thought the temp of water coming from the water pump would indicate if the engine is running hot or not but I guess that's the wrong assumption then. can the thermostat be by-passed to check if that's the problem? If it can be by-passed is the any harm in doing that?

Thanks so much for your help. You seem very knowledgeable about this. Are you a boat mechanic?

 

[pilot10010]

Re: 1996 90HP HOT light comes on

One more thought. The reason I thought the water would be boiling is in a car when the engine heats up the water in the radiator also heats up a great deal or even boils. Is it not the same?
Thanks.

 

[tashasdaddy]

Re: 1996 90HP HOT light comes on

car is a closed (sealed) system, outboard open system.
you can remove the tstat, and try it. but better off is to suspended the tstat in a pot of water, and using a candy therometer, notice when the stat start to open and when it is full open. start 140* range, full open by 160*. also while stat is out. flush the system. your 90 may have 2 stats, one for each bank.

 

[pilot10010]

Re: 1996 90HP HOT light comes on

We'll try that. Thanks so much. Any other suggestions are welcome.