1989 100hp Johnson cooling issue?

[Fishindan]

Hello all. New member here.
Just purchased an older 17.4" McKee craft flats boat with a 1989 100hp Johnson. Model# J100STLCEM.Fellow I bought it from said it was a 115 and cowl even says Evinrude 115, but data plate should not lie.
Guy ran it in his yard and even took us out in the river. Eng. ran fine.
A week after getting it home decided to see if I could start it. With hose hooked up to cuff, started and ran @ idle for a few minutes. Had water coming out of pee hole. Warning horn came on. Shut down eng.
Tried again the next day and kept feeling the cyl heads as it was warming up.
Found the rt. side (aft looking fwd) was getting a lot hotter than the left.
Again had water coming out pee hole.Shut down before horn.
I know it shouldnt make any diff. but I had the cuff with the hose connection hooked to the left side. Should it matter?
It seems a big coincidence that it ran fine when we took it out but wanted to overheat in my yard a week later.
I plan on rplc the water pump for routine mtc.
Do you guys think this is a good start?
Do you think it might be the cooling passages?
I am also planning on buying a service mnl. for it.
Thanks for any help.

 

[Fishindan]

Re: 1989 100hp Johnson cooling issue?

Anyone have any suggestions?

 

[emdsapmgr]

Re: 1989 100hp Johnson cooling issue?

Your engine model is a 100S. The "S" models typically put out 10% more hp that is stated on the serial tag, or 10% more hp than 100. It does not matter how you hook up the flushette on the lower unit. A strong telltale stream does not mean that the powerhead won't overheat. That engine has two thermostats, one for each head. If one of them is stuck closed, cooling water will be prevented from exiting that side of the block and that head will overheat. I'd suggest you pull the thermostat housing apart and replace both stats.

 

[kenmyfam]

Re: 1989 100hp Johnson cooling issue?

Water pump service should be done if there is any doubt as to it's condition.
Stats should be checked and replaced as necessary.
Is this a salt water motor ???
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