Overheat Alarm

R

ranger

New member
Hey, Maybe someone can give me an idea. Yesterday I took off from the dock and went about 3 miles down the Cumberland river. Boat was running well. My overheat alarm in the control box went off. I immediately shut down the motor and waited for it to cool. When I started it back up the alarm was still going. I was getting a good constant stream from the telltale hole and the heads were hot but I could touch them. I hated to do this but I had to run it back to the dock. The motor would not go over 2000 rpms, but it ran well (I didn't hear things coming apart) and we made it to the dock. It even started back up and went onto the trailer ( the horn was still going). Today I went out and turned the key and the horn was quiet.
I put the muffs on and let it run for about 30 min. No horn.
Water felt cool coming out. I started it up again and the horn started sounding. I fell the water again and it was hot. I pulled the thermostats and they looked like they had seen better days, so I will replace them.
 
Oops hit the post button too quick. What I wanted to know was do any of you have any ideas on this slight problem. Its a 1979 Johnson 200 hp V6. Thanks
 
you may have a defective temp sender,that puts the engine into a safe mode(low rpms) so you cant do any damage ,but get the boat an passengers to a safe place
 
as i know of the old Johnson Evinrudes didn't have a safe mode for low rpm's. check your compression and make sure you have good or close compression on all cylinders let us know what you find. 79 motors were cross flow motors. Should have high compression like 115 to 130 on all.
 
ok let me tell you something
i have a merc and it hasd the same problem but it was the switch box
what would happen is the alarm would go off and the motor would be cut in have the speed i mean i would lose half the cylinders and i thought it was a safety feature but it wasnt it didnt come with that feature its a 1988 150 so i opened up my repair manuel and diagnose it myself and it turned out to be the outer switch box check it out your self when the alarm goes off see if you lose half the cylinders good luck
 
Update. I installed 2 new thermostats. The old ones looked like they were barely working. Ran her for about 30 min (turning it off and on). Heard no alarm or abnormal sounds and I could get full rpm. Seems like the simple solution was the best solution. When this rain stops I can test her on the water. Thanks for the replies.
 
hey wanna ask you something
the alarm is it a long beep like this beeeeeeeeeeeeeeeeeeeep
or does it sound like this beep beep beep beep beep
i know it sounds crazy but there is a differance ill bet its beep beep beep
b eep
 
It was a long beep. It came on and stayed on. Even whenI shut it down for 30 min. or more like the manual said, iy came on and stayed on.
 
The same thing happpened to me yesterday. The alarm came on - for the first time about a half hour away from the slip. I shut down, waited a few minutes, restarted and it would go a way for a while. I unfortunately didn't know what it was for a little while. The engine only has a few hours on the rebuild, so the t-stats should be fine. There was a water stream and the engine wasn't at all hot to the touch. It was on and off until I got back to the dock. Could this be another problem?


Carl
 
Mine did go off again yesterday, but everything was okay with the motor. When it went off, my wife said to do what I had to do. She told that if we need to get another motor, now is the time to find out. So, I ran this motor at full speed at least 5 miles up the river and 5 miles. I did everything to make this motor seize or blow up. Then all of a sudden my wife looked at me and said turn it off an pull the key all the way out of the ignition. She then waited for the hour meter to stop ticking and counted to 60. She told to put the key back in and crank it. I did and we went the rest of the day with everything running great and no horn going off. She said that she had remembered that when her dad owned the boat shop, the mechanic had showed her how to reset the system. I had put in the new stats but had not reset it, so the engine still thought it had a problem. ;D
 
Ranger...w/a wifey like that, who needs an OB Tech... 8)...that's as good as marryin' a girl who's daddy owns a COLD-BEER PARTY-SHOP!!! ;) ;D...
 
She's LHMFAO right now. I think she's a keeper. When its comes to fishing, hunting, boats and trucks she's out there before I am. She helps me work on them too. ;D
 
How can ya tell what temperature the thermostats are rated for? I replaced both yesterday and the guy asked me what temp are they? It is a rebuilt merc 150 (1988) and I don't really know. He gave me t-stats that are rated for 130 degrees and said they should work fine. Do they have markings that tell you, or do ya just have to know (look in the manual)

Also, what temp does the high temp alarm go off at?


Thanks


Carl
 
thermastas 143 degrees
imtelling you check the sitch boxes this problem is going to drive you crazy
the next time it goes off[and it will] you said the motor rpms cut down, there not supposed to do that m, pull a wire from one spark plug on the port side and hold it close to the plug and see if your getting a spark if you are do the same to the starboard side
remember you have two switch boxes an inner an outtewhen i had that problem it was with my low oil alarm going off and i changed everything
finally i got it right
the switch box
 
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