False overheat alarm, I hope! Other causes?

[Black85L98]

I have a Mercury 90 HP 3 cylinder motor #OC235421. I am having some problems with it and thought you folks may be able to help. The oil level sender is bad and disconnected but it is not causing a problem as I check the level before each use. My problem is that the shifter is sounding an overheat alarm. A long steady chirp. It starts when the key is turned on and never goes off. Cold or warm it is the same. The tell tale tube is pissing at idle and has a good stream at 5K RPMs. Motor runs fine except it is a little rough at idle. There is a black wire going from the left side of the block to a small black connector on the right side. A brown wire from a control box is attached there also. Disconnecting the brown wire stops the buzzer. <br /><br />What’s the problem? <br /><br />Thanks<br />Rick

 

[kev_alaska]

Re: False overheat alarm, I hope! Other causes?

Sounds like you have a ground fault somewhere. Check all the wiring and replace any that looks funky..

 

[The Marine Doctor]

Re: False overheat alarm, I hope! Other causes?

Test the lead from the sending unit to ground. If there is continuity...replace the sending unit.<br /><br />Do this test when the engine is cold.<br /><br />TMD