87 50hp johnson Overheat Alarm

After running it on muff's for about 15-20 minutes, the overheat alarm went off for about 3 seconds, then it stopped. I ran back to the throttle box and turned the engine off, after it sat for about 20 seconds, the alarm went off again. There was plenty of water pressure, and the pee hole was peeing like crazy, but the water comming out of it was no where near warm. I touched the head, and it was quite warm, but it didnt burn my finger but it would hurt if I held it there for longer then a second. I replaced the thermostat, and pressure release valve, head gasket, water pump, and cleaned all the water passages with a wire brush. Is this anything I should be concerned with? What would you reccomend?

Re: 87 50hp johnson Overheat Alarm

Was the top of the t-stat vented Goldfish? Little "V" notch in it. BRP stats don't got them so I cut them in with a dremel tool. Sierra's are vented. But man is that stat a pain to get to. <br /><br />You should be able to lay your fingers for several seconds on the flat place on top just forward of the head at idle. If you can't, I'd worry about it. My 85' 50horse does that once in a while if I'm idling looking at the depth finder. Usually I shut it down and let it set for a while and it's OK. Not a fix for sure. I'm thinking about moving the tell tale connection to the top of the exhaust housing.....if I can get the toon off the wife long enough.....

Re: 87 50hp johnson Overheat Alarm

Im pretty sure it is not vented, I replaced it with a mercruser tstat, the shop said it was the same thing. I was also thinking about moving the tell tale to the top but I never did (I had the powerhead off and everything :-/). What exactly has to be cut/ground to allow some water to flow through the thermostat, or should i just drill a small hole through the pressure release valve?

Re: 87 50hp johnson Overheat Alarm

The stat should have a little flate plate on top that opens when it gets hot enough. I just push it open from the bottom and hold it open with a little screw driver while I cut the V notch in it.<br /><br />Check the picture in the link below. The first stat...you can just see the notch. On the second page is a little better pic.<br /><br /> http://www.iboats.com/mall/index.cg...d&keywords=Thermostats&submit.x=33&submit.y=5

Re: 87 50hp johnson Overheat Alarm

A notch like this?<br /><br /> webpage<br /><br />Also, shouldnt the thermostat open before it overheats? Or is it not opening because there isnt any waterflow near the thermostat? Thanks again obj!

Re: 87 50hp johnson Overheat Alarm

Yea! that's it. The stat should open for increased water flow through the engine once the temp gets right. The vent helps let any air outta' the engine so the block stays full. That's one reasone I'm going to move the tell tale connection to the top of the exhaust cover...Help let the air out once the engine is started.