75 Merc continuous beep alarm

[92python]

My 12 year old 75 Merc has an occasional problem with a continuous beep. I think that is the overheating alarm.

It is spitting water fine, running normally, and if I turn the motor off, then back on the beep goes away for a while.

I am guessing I either need to look at a sensor, or impeller but those are guesses.

Does anyone know of a mechanic in the West Metro to diagnose and fix the problem or have any tips to do it myself?

I do not have a manual or other documentation for the Merc. Is there something out there like a Haynes or Chilton for Mercs?

Thanks.

[mnrstrider]

Oil injected? could be the low oil sensor too...

[Surface Tension]

Yes you can get a manual for Mercs.
Start your troubleshooting by replacing the impeller, it has to be done anyway.

[fivebucks]

You can get a manual at the library. It sounds like it could very well be the impeller. That's not too bad of a job following a manual. With a little mechanical skill you should have no problem. I just make sure I leave myself plenty of time.

[MercMan]

If the oil level is fine and the engine still beeps full time, but water is coming out of the tell-tale hole it is either low water pressure (water pump/impeller) or the temp sensor is stuck. I had a 1987 90 horse Merc that did the same exact thing. Ended up being the sensor. At any rate, if you're uncomfortable with troubleshooting this yourself, take it in. Don't mess with overheating issues. It could damage the engine big time.

[Borch]

Replace the thermostat while you're at it. One or the other will likely take care of your problem. If not it may be your sensor. Likely culprit is ranked order are:

#1 Impellor

#2 Thermostat

#3 Sensor

Good Luck!

Borch

[E.Martin]

I had a '94 60HP that did the exact same thing. It would beep if I was trolling, but not at full throttle or idle. I found out that the high temp sensor is set to a very low temp, so that when the impellor gets a bit worn, the flow rate will drop and your temp will rise slightly, thus initiating the alarm.

Does yours beep when it is cold? If so I would first check both the oil level and temp sensors, since a high temp condition wouldn't be reached until the motor has been running for a while.

[Fish Head]

I had the same problem with my '98 60hp. It would beep if I was trolling very slowly for a period of time. The Marine repair place said it was my water pump (is that the same as the impeller?). I had them replace the water pump and it hasn't happend since.

[Guest]

Echo what has been said. I have a 2002 125 Merc that was doing the same exact thing. Seemed to be spitting enough water, but had the impeller and thermostat changed and haven't had the problem since.

Couple things: Too expensive for what was done. Next time I'd do it myself. Sounds like it's not all that difficult. The other is the fact that it sounds like the sand tends to be the culprit. Digging up too much sand too often tends to hasten the problem. Lessen learned, and I'm back on the water.

[92python]

Thanks for the replies.