Merc. alarm horn frustration.
 

OK.. Engine is a 1991 Mercury 200 HP 2.5L. Converted to Electronic Oil injection.
When I got the engine the PO told me that the engine ran fine but then the horn started sounding whenever it was started up or at idle. As soon as you gave it some gas the horn stopped... and I found that to be exactly the case. Engine is a screamer, and I've never had any problems with it other than the horn. Water pump is replaced every other year, tattletale stream is forceful and constant. Thermostats were replaced 2 years ago. Mechanical Oil injection was replaced with an electronic oil injection system 2 years ago. Engine was lengthened from a 20" to a 25" when I hung it on the back of the V21. Cold and warm compression numbers are all within 5 lbs of each other on all cylinders.

But

The damn horn continues to sound. Constant sound as soon as you turn the key, not a series of dots or dashes. Anyone have any idea what the hell is causing the problem, or at the very least how to fix it? It's really getting to me and truthfully I don't want to trailer the damn thing down to Spare to have him fix it. (Not that I don't want him to, he's the only guy I'd trust that's semi-close by. I just don't want to make that trip twice). (once to drop off the boat and once to pick it up)

D, according to the manual on the 2.0, constant beep is overheat and intermittent is oil injection. When u turn the key on ,should get a long and 3 shorts. This is the systems self check. I think that is controlled by the oil alert module. That's what went south on mine and didn't alert me to the low oil in tank. Maybe spare or ferm know of a way to test it.

Did u have to bypass any of that when you installed the electronic. Oil pump.

Did you install the longer tube for the water pump for a 25 inch leg?

the alarm module is bad

Need to isolate it out. I would unplug the oil injection warning module and see if it stops going off. If that doesn't do it, unhook the overheat sensor(s). Just have to work your way down the chain until you find the problem. On an older engine, it could also easily be corrosion making continuity occur where it shouldn't.

Yes. Engine gets plenty of cooling. The pisser flows a good strong stream that gets warm after the engine warms up.

Was sorta thinking the same thing, but wanted opinions before I spent $$$

No, when I turn on the key I get one continuous sound, no beeps.

The Electronic oil pump just replaces the mechanical one. None of the installation bypassed those systems.

The horn sounded before I put in the electronic injection, just went away after the engine speed increased so I lived with it. but now it's constant no matter the speed. This (the constant sounding) all started after it came out of it's winter slumber this year.

Ok, will start doing it by the numbers...

THANKS TO EVERYONE for their suggestions... I'll keep everyone informed as I work thru it.

Should be 7 wires on module

White & blue/white. Pump motion sensor
Black. Ground
Brown. Temp sensor
Blue. Oil reservoir
Purple. Power supply 12 vt
Green. To switch box