1987 merc 175ob overheating horn

[pooleman]

I recently purchased a boat with a 175hp. When I take the boat out, after about 5 minutes of run time at 3000 to 4000 rpm the warning horn goes off. I shut the boat down and right away I can restart the motor and go again for another 5 minutes or so. The horn doesn't go off at trolling speed and doesn't go off all the time. Water flow from pee hole is a solid stream. Is the problem a sensor or a short in the wiring?

 

[abacoguy]

Re: 1987 merc 175ob overheating horn

Sounds like your problem is similar to mine. See yesterday's posting for '96 225 Merc. overheating. Maybe someone can come up with a suggestion. I have a full manual and there is a suggestion that if the seal on the impeller isn't placed just so that air can get in causing overheating. I plan to put new impeller, seals and thermostat next weekend. Will let you know if that works. <br />Abacoguy

 

[mellowyellow]

Re: 1987 merc 175ob overheating horn

welcome aboard,<br />might be a good idea to install a new impeller to<br />start to be safe.<br />pick up a service manual, it has the test proceedure<br />for the switch.<br />good luck,<br />M.Y.

 

[trumanlake]

Re: 1987 merc 175ob overheating horn

Do you have a water pressure gauge? For a small investment you can diagnose some cooling problems alot easier. (excuse me for shouting) GET ONE