I have repowered with brand new 496ho. These engines have a little over 20hrs. Coming across the lake this past weekend, engine alarm goes off after about 1 hour of constant running at 3800rpm. Shut down both engines. Drive oil, engine temp,oil pressure perfect in both engines. Restarted engines, no alarm sounding. Ran the boat back to the marina about 2hrs at same rpm. Alarms do not resound. Any ideas?? I am puzzeled. Did think that I heard a misfire, but the other folks on the boat said they heard nothing. Should I be worried?

Was it a solid BEEEEEEEEEEEEEEEEEEEEP, or a BEEP-BEEP?

The solid beep is for what you mentioned above. All other codes will be an intermittent beep-beep.

I'm going to guess it was your MAP sensor. I've had that happen before.

I recommend anybody with 496's to buy a scan tool or diag software. Don't waste time guessing what the problem is.

Solid beep. Shut down engines immediately.

YOu said engines(s)

Both engines shut off or is that a typo?

engines wont shut off,,,solid beep is full guardian mode,,,youll only be able to idle the engine,,500 600 rpm,,,he said engines,but probably shut both off,when he heard the alarm

Heard the alarm, shut down both engines. Was not sure which engine alarmed. Boat did not go into guardian mode. Ran the boat yesterday, everything ran as normal. Engines have smart craft monitors, and everything checked out both visually(fluid levels etc) and on both the digital smart craft gauges and analog gauges for both engines. Stumped.

If there was a beep then there should be a code history even if the code is no longer active...

Constant tone alarms are for:
1.) engine coolant temp overheat,
2.) low engine oil pressure,
3.) engine overspeed,
4.) exhaust manifold cooling temp overheat
5.) sea pump PSI low FYI This is kind of commen, And is said to not show up in the history. The only way to know is to watch this sensor live as it happens. Make sure all you grounds are tight on and around the engine. And if this sensor has any paint on it it could be loosing it's ground and sounding the alarm.Or you could have picked up some air bubbels for a short time till you slowed down, Or the impeller, or impeller housing is starting to fail. This is Just a thought of what could be happening is all.Good luck with it.

Constant beep alarms are for:
1.) low outdrive lube level.

Two Alarm beeps every 60 seconds are for:
1.) Faulty cam,
2.) IAC,
3.) MAP,
4.) MAT,
5.) knock sensors.
6.) open/short in the engine cooling temp circuit
7.) open/short in fuel injector wiring circuit,
8.) open/short in oil PSI circuit,
9.) open/short in exhaust manifold cooling temp circuit,
10.) open/short in sea pump circuit,
11.) open/short in throttle position circuit

Thanks for the info.