control box squeal

[BD Rod]

I have a 1987 90 hp mercury ouboard and I just turn the key ,without starting it, and a high pitch tone comes from the control box. Any advice? Thanks,Rodney

 

[j_martin]

Re: control box squeal

Either the temp sensor is shorted, or the oil control module is bad, or you have a wiring short in the alarm circuit.

You need to go at it with an ohmmeter and a wiring diagram.

hope it helps
John

 

[BD Rod]

Re: control box squeal

Thanks. It was strange that everything was working fine then I tried my bilge pump and it wouldn't work so I shook the pump and hose,went back and flicked the switch a couple of times then the bilge sarted working so I turned the key to the on position and now the squeal. I drove across the lake,about 5-10 minutes, and everything worked ok but still the squeal.So if i see a short across the sensor with it disconnected then it's a bad sensor?

 

[j_martin]

Re: control box squeal

Thanks. It was strange that everything was working fine then I tried my bilge pump and it wouldn't work so I shook the pump and hose,went back and flicked the switch a couple of times then the bilge sarted working so I turned the key to the on position and now the squeal. I drove across the lake,about 5-10 minutes, and everything worked ok but still the squeal.So if i see a short across the sensor with it disconnected then it's a bad sensor?

Get a maintenance manual for it. Preferably a mercury manual. In it will be the wiring diagram.

The oil system monitor (oil alert) and the temp sensor share the same alarm circuit. Something is shorted, either in one of those 2 items, or in the wiring itself.

It is probably significant that the alarm went off when you restored power to the bilge pump. Perhaps they have a common power source. Power for the alarm circuit is supplied by the controls, and in some boats that all gets cross-wired.

When you turn on the key, you're supposed to hear a short series of beeps indicating the oil alert module is operating normally.

hope it helps
John

 

[BD Rod]

Re: control box squeal

Thanks for all the help. This is the first time I heard any sort of alarm noise. I never have heard the beeps telling me everything was ok when I turned the key on. I just bought it last fall and have only used it 4-5 times so far this year. Rodney