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1989 150hp overheating on muffs?

bill_w

bill_w

Advanced Contributor
I ran this 1989 150hp Johnson motor all year, with no trouble, except the reg/rectifier wasn't working, so the battery didn't charge. Once I pulled the boat out for the year, I changed out the regulator/rectifier, and test ran it on a set of muffs. The motor is now charging, but while it was running on the muffs, near idle speed, it overheated on the port side. I know it was the port side because if i disconnected that temp sensor, the buzzer went off. Also, just from holding my hand on the block, there was a large temp difference between the port and starboard sides of the block.

There was a good stream of water from the 'pee' hole, and water was coming from all of the usual holes on the lower unit. So, why would it run great all year, then overheat after being out of the water for a couple of weeks? Could a thermostat have stopped working, and stayed in the closed position?

thanks in advance
Bill
 
Do you run the mtr in salt water?? It could be the thermo or maybe the water deflectors in the block. If it was my mtr I'd put it back in the water and try it before running off in the heat of the day.
 
OK, not salt water...none of that near me. And Joe, not full blast, but enough to keep water spilling from the cups when the motor was running. I know that I have a 72 50hp Johnson that WILL NOT run on the muffs...it will overheat unless it's in water. Wondering if the 150 is the same. My 115's are ok on the muffs though. ???????
 
Normally the water must be turned on full force otherwise the water pump (if in proper condition) will draw air and overheat. Put the muffs in a vice and close them up somewhat so that they really have a grip around the water intake holes.

Thru my years of experience, the engines that will accept the ear muff type flushette from the 50hp model up thru the highest hp range, had to have the water on full force otherwise I encountered problems such as you mention. This is not to say that a problem might not exist with that engine.... just my experiences. Of course the smaller hp engines did not require as much water being fed to them.

At any rate, let us know what you find... pump failing, water deflectors swelled, couple frogs in the water passages.
 
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Hmmm....frogs??? I guess if tadpoles grew up in there, cause I don't think bigger ones would fit through the little mesh screens on the intakes. But I like the idea Joe. Take it to a mechanic, have one leap out at him when he pulled the thermostat cover. Now that would be worth a couple of laughs.

Anyways, back to being serious. No, I've never tried it running a hose at full blast. All I have ever read says 'don't do that' because you will pressurize the system, and maybe compensate for a bad impeller. The 50hp drove me nuts, I did a pump rebuild just because I didn't know the last time it had been done, then it overheated everytime I tried to run it on the muffs. Racerone suggested I try it in the lake, but I used a 1/2 50 gallon drum. Worked fine. I'll try the 150 in the spring, I've winterized the fleet for now.

And Boobie, I use a flusher with the water coming in from both sides. It didn't make sense to get one that only fed one side.
 
Just thinking again...I have 2 115's, a 1980 and an 85. Both of these run fine on the same muffs. Whatever, I'll figure it out in the spring. I was more or less just wondering what might be causing it to overheat suddenly after running fine all year, and have an idea what I was facing for repairs in the spring.
 
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