Overheat Alarm

[Oil]

I was returning from a day of fishing and a mile from the marina the alarm on my 60hp Merc went off. Steady noise. I was keeping an eye on the telltail and it had been very strong all day. After 20 minutes I restarted the engine and almost made it back, but the alaem went off again. Used my trolling motor to take me the rest of the way. What would cause the engine to overheat when there was a strong stream comming out? Engine had plenty of oil so that was not a problem. Any thoughts?

 

[WillyBWright]

Re: Overheat Alarm

Welcome to iboats.<br /><br />What year is that motor? If you don't know, post the serial number. You could have a bad sensor which is rare, a short someplace between the sensor and the alarm which happens sometimes, or you might have a bad horn. I tend to doubt that because those typically sound as soon as you turn on the key, even if the motor is cold. I think the alarm system is doing it's job. Your motor is running hot.<br /><br />So, there are a few possibilities. A weak water pump which doesn't seem to be the case. A sticky thermostat which is definately a possibility, or scale build-up in the powerhead preventing good heat transfer. Motor could be running lean ot the timing might be too advanced. Have a look at the sparkplugs. They should be brownish with a slight gloss to them from oil residue. If the thermostat is sticking, you can clean it with vinegar overnight. Where are you at? Elevation can affect that too.

 

[Oil]

Re: Overheat Alarm

Originally posted by Oil:<br /> I was returning from a day of fishing and a mile from the marina the alarm on my 60hp Merc went off. Steady noise. I was keeping an eye on the telltail and it had been very strong all day. After 20 minutes I restarted the engine and almost made it back, but the alaem went off again. Used my trolling motor to take me the rest of the way. What would cause the engine to overheat when there was a strong stream comming out? Engine had plenty of oil so that was not a problem. Any thoughts?

 

[Oil]

Re: Overheat Alarm

Motor is a 2000 and the water pump was replaced in 2003. I live in Kentucky, but half the time I use the boat in Florida saalt water. I bought the boat/motor used, so I don't know how it was cared for by the original owner, but I always flush it after being in salt water, using salt away in the flush. Thanks for any info you can give me.

 

[kmac]

Re: Overheat Alarm

I have had a similar problem. The horn has gone off erratically-some times when the engine is cold and somtimes not--seems to be how you hold your mouth. I have done some trouble shooting following the instructions in the shop manual and I am in the process of replacing the sensor. I just bought it and have yet to put it on. But, it seems as though you have the same problem--do you have a manual

 

[Oil]

Re: Overheat Alarm

Don't have a manual. I just took the boat down to a local mechanic and he said he would replace the pump and thermostat, and blow out the lines. I'll let you know if this helps me.

 

[BJM]

Re: Overheat Alarm

On my 115 Mariner the module went bad. On mine the module sounds the alarm for both low oil as well as overheating. It went off in the middle of a lake for no reason. Tell-tale was strong and not too hot. I never figured out why but the new module fixed it. The sensor tested out fine.

 

[kmac]

Re: Overheat Alarm

Mine is also the module not the sensor as I said earlier---sorry