Overheat alarm

[Tommygreeneyez]

I have an 87 Yamaha 115 115ETLH, and today when I was out on the river I started getting an overheat alarm when I was at full throttle only. I would shut it off and then when I turned it on the alarm was still there but as soon as I increased throttle it went away and stayed away..until I went WOT then it came on after about a minute...It was shootin water out the tell tale same as always..so Im not sure whats wrong...I pull the releif poppet out when I got home and it didnt fall out freely when i removed the spring...but it wasnt jammed in there. as soon as i grabbed it and pulled it came right out..so i dont know if that is the problem..I am assuming the imellor is fune because of the water coming out of the hole strong. Any ideas here..and where are the t-stats on this so i can check those...Im not strong on 2 stroke engines but I work on car engines all the time..so i would assume it was a tstat sticking, but why would the alarm go away and them come back..any help would be appreciated

 

[tunaguymarlinfisher]

Re: Overheat alarm

The therms are on the upper part of the cylinder heads, I would check/ replace water pump if it has been over 3 years since it has been changed. I always change them both at the same time and also clean the relief valve like you did. If that doesn't help you might have a blockage under the pick up screens or at WOT there may be a flow problem where there is not enough water near the pick up screen.

 

[Tommygreeneyez]

Re: Overheat alarm

Well I checked the tstats and they both open up in hot water, i ran it on muffs and the pee hole is shootin water with no problem, I couldnt see how to get to the waterpump, I am assuming I have to remove the lower end to get to it...I have a shop manual coming from yamaha I will wait until I get that, I also checked for blockage on the intake screens, there is no evidence of blockage anywhere i could see, poppet valve, tstats, all those passages look clear and feel no scale build up. I am assuming it has to be a water flow problem , because the alarm came after a day of tubing and I think all the turning might have caused the intakes to not take enough water, and when I was running it into pull out It hadnt cooled down all the way so at WOT it would get very warm. I am not too worried right now, I checked all the stuff and it seems to be working ok, so unless I have another problem I will chalk it up to not enough flow while we were tubing...

 

[tunaguymarlinfisher]

Re: Overheat alarm

You didn't say you were pulling a tube..... you had been lugging the engine. That is more than likely the cause.