Help! Double-beep from ECM

[Beer-30]

My stock 2001 496HO keeps beeping at me while underway. Idling, at speed, or KOEO, I get a beep....1 second pause.....beep. It happens every minute or so. Real annoying. All fluid levels are full. The guy I bought it from said it has been doing that since it's last dealer performed service. He thought it was the depth-finder, which I have replaced and found that it is the ECM warning alarm that is making the noise. I plan on checking to see if the plug for the drive lube sensor is maybe unplugged (?).
I bought the service manuals for the engine and drive from Mercury, but it doesn't address this situation.
Anyone have any ideas?

[PHX ATC]

Drive lube might be low or indeed, the sensor might be off whack.
Way back in the day, when I had a boat , I went through this whole ordeal with the same issue. Turned out, it was a cam sensor and crank sensor that had 2 or 3 of the prongs bent back. Seems it would make good contact while idling and slower speeds, but as soon as it got over 3000 rpm, it would be intermittent, beep, and freak out the engine.
Check all the connections. All those little prong thingies in the wiring harness. If they took any off, have them recheck them with a fine tooth comb. There actually is a bulletin at the Merc factory that comes from my story. It has the entire wiring harness checked at all the sensors to ensure the little prongs (all of them) are hitting and functional. It's on their trouble shooting guide at the factory now too.
Good luck.
PM me if you've any detailed questions.
Toby

[shockwavebd]

It could also be your water pump impellar going bad

[Beer-30]

Thanks PHX ATC, wouldn't want to fly into IMC being a VFR pilot, eh? Thank, I'll check the vectors you suggested.
Shockwave, does the impellor have a sensor? or do you just mean temperature. Because temp is normal.
I have a strong feeling it could only be that they didnt plug the drive lube sensor back in after servicing. He had just taken it in to Sleek in PHX for a full service and said it beeped since then. That should be about the only thing they touched during a service that has a sensor.
I will check all I can next time the hatch is up. Runs great, though!

[charlyox]

:hammer2: My 496 H.O. did the same thing. I'll have to look over my recipts because I can't remember what it was.

[Beer-30]

Thanks, Charlyox. I know it has to be something simple. If it was major, it wouldn't run so good!

[Faster Daddy]

For peace of mind I'd have someone throw a scan tool on there, its too expensive a motor to be guessing.

[Beer-30]

You're absolutely right, Faster. Or shall I call you Daddy?
After I check the lube monitor plug, and if it is in good shape, it's off to the local Mercruiser dealer to slap on the scanner.

[phebus]

Since you just had it serviced, my money says your right on with the outdrive lube container plug. I bet you find it unplugged, or just not fully seated. Too coincidental, the servicing and the beep.
I agree with the scan, only if that is not the obvious problem. Why throw away good money.

[Beer-30]

Thanks phebus. By the way, I will post findings. Probably check the monitor today, so I will let you all know if it was the plug. If I end up having it scanned, I'll post those findings. Never know, it could happen to someone else later!