OverHeat Alarm

[dhughes49]

1996 johnson 150 saltwater Ocean Runner

We used the boat all weekend and it ran just fine. We ran out to a reef that was about 2 miles at high speed and it seemed fine, then when we started to idle over to a flat maybe 1,000 yards away, then the over heat alarm sounded and started flashing red. I killed the motor to prevent any damage. We fished some so it could cool down and we ran at high speed to another spot and it did ok... then we tried to idle to the spot that we had been going to (the reason we did this is because we thought it was low oil, it ended up us finding out that the buzzer sounding was the overheating one) then it buzzed again with the over heat light and we immediately killed it. At that point we knew it was time to get out of the water so we hauled back to the marina and put our boat up. It basically doesn't overheat at high speeds, only when we was idling to the fishing spot.

It is pee streaming just fine, and was not hot. It has a brand new empellar


The day before we had ran into some kind of mud silt patch and it bogged the motor to the point of it stopping it. Could it have sucked something up that is partially blocking water flow to the engine or something like that?

 

[Solittle]

Re: OverHeat Alarm

You have the solution - - why the post?

 

[boobie]

Re: OverHeat Alarm

Yes it could have. Pull the theromostats out, start it up on a flusher and see what comes out.

 

[dhughes49]

Re: OverHeat Alarm

Thank u boobie for this useful comment. and solittle i post this question because I'm new to boat moters and im not sure what the solution is or even if that could cause the problem. Im Just tring to give good info so i might get back good info. thank yall for both post

 

[Chris1956]

Re: OverHeat Alarm

Impellers can be torn up such that the motor will overheat at idle and cool fine at speed. If the flush doesn't fix it, check the impeller.

 

[seahorse5]

Re: OverHeat Alarm

Those motors use a plastic capsule with the thermostat inside of it. There are a series of holes in the capsule for the water to flow at low speeds. If sand, shell, weeds, etc. block off all or some of the holes, that cylinderhead will overheat only at low speeds. At higher speeds, the increased water pressure pushes the capsules off their rubber seat and water flows around them so the motor will not overheat in that situation.

Pull the thermostats and inspect the small holes for debris. A thermostat could be sticking and give the same symptoms.

 

[dhughes49]

Re: OverHeat Alarm

I think I will pull the thermostats and replace with new (due to their age). I want to be clear on what boobie said ..... do i need to start motor on a flusher with the thermostat cover off and the tstats out to blow out any debris still in motor ? If so how long do i let it run ? a few seconds or a few minutes ?

 

[seahorse5]

Re: OverHeat Alarm

30 seconds of run time should do it, unless you see more debris coming out of it.

 

[dhughes49]

Re: OverHeat Alarm

ok thanks seahorse5

 

[dhughes49]

Re: OverHeat Alarm

ok i pulled out the thermostate ands heres a pic .I asume that the older looking one that is completely closed is my problem. I have ordered new ones but they are not here yet . Can i use my boat this week end without the thermostat or is that a bad idea?
well i couldnt get the pic loaded for some reason but one tstat is open and one is completely shut. ill try again later