Audio Alarm

"I have a 2005 Merc 350 mag EF

"I have a 2005 Merc 350 mag EFI, bravo III. Bought new in october 2006 she has 23 hours total time on her. Last outing the audio alarm started going off at 2500 rpm. the oil preasure/water temp gages read 40/175. This is no change since first hour of operation. The out drive oil tank is full. If I try to go above 2500 rpm the rev limiter kicks in and starts cutting out the engine. If I pull it back to neutral the audio alarm goes off. I can then go under power again as long as I do not exceed 2500 rpm.

Any ideas as to what the problem could be? how to diagnose it? and fix it?"

"Sounds like a bad alarm sendi

"Sounds like a bad alarm sending unit. I'd start with troubleshooting the temperature alarm sending unit.
The water temp that the gage is indicating is not necessarily the the exact temperature at the temperature alarm sending unit. The slight increase in water temperature with higher revs may be enough to trip the switch.
I'd recommend buying a hand held infra-red thermometer. Sears has them and they're fairly cheap. It comes in very handy in situations like this.... helps figure out which is really bad, the switch or the gage. But if I had to guess, based on the fact that it's a new boat, and there isn't any other indications of overheating, it's most likely the temperature alarm sending unti.

The easiest way to troubleshoot this one is to disconnect the wire to the alarm sending unit and see if the problem persists. If it does, reconnect the wire move to the next switch (oil pressure or lower unit oil reservior). Just make sure you only do one at a time."

I had the same thing happen to

I had the same thing happen to me last year on a new complete repower. My mechanic said not to worry about it so long as i have good oil pressure water temp and drive oil in the resivoir. Mine use to be a faint alarm and get louder the longer i drove. When i stopped the alarm stopped.

"update: I bought a rinda sca

"update: I bought a rinda scan tool. i took the boat out for a test drive. at 2500 rpm the audio alarm went off as described above. faults showed "gardian strategy 47 seconds"..."low oil presure strategy 50 seconds"..."overspeed 26 seconds". the oil presure gage still shows 40 psi.

i plan to hook up a manual oil presure gage to the port where the oil presure sender is to check the oil preasure. i think the sensor is bad but i need to verify it.

i have found out there is two oil presure sensors on the motor. one runs the gage(single wire) and one runs the PCM555 computer (three wire). i do not know what the "overspeed" fault is though.

any other ideas for these issues?

thanks, kirby"

"UPDATE: Removed oil pressure

"UPDATE: Removed oil pressure sensor and attached manual oil pressure gage at the same port. gage read 45 psi at idle, warm. so i need a new sensor part number 881879011, $92.07. now i just have to find one.

thanks to everyone for their help...kirby"