Help - Can not figure out alarm

[SC_Regal]

I have a problem which started recently ( I'll try to give as much info as possible):

New SEI out drive, 2000 Mercruiser 5.0 EFI sn# 0L707235 on Regal 2500 LSR used mostly in salt

when I get on plane I get an alarm, the alarm sounds every 4 seconds and lasts about 1 second and will continue until I stop (turn off) engine. It will continue at idle. When I re-start, no alarm until I get on plane for about 30 seconds. The temp gauge reads 170-175, oil pressure 40-60 and remote outdrive oil reservoir full. I disconnected the the outdrive reservoir sending unit - no change; disconnected the oil pressure sending unit and the low pressure switch - no change; disconnected the temp sending unit and the high temp switch from the t-stat housing - no change.

I just pulled the boat out of the water and ran on the muffs for 30 min with no alarm. I checked the engine temp with IR gun and got the following results (did not have the gun with me on the water when alarm sounded):

T-stat housing: max 145, usually 125-130
block under T-stat: max 165, usually 145-155
starboard manifold: max 200 at small spot top and forward" rest of manifold never got above 190, usually 155-180
port mani: max 145, usually 115
starboard elbow: max 150
hotest temp on block: 175-180 on the freeze plug starboard/forward

no alarm with above and the alarm sequence at start-up is working .

I'm confused - I disconnected the 3 sources of the alarm (per wiring diagram and searching) while it was sounding and it did not stop. That would leave two possibilities (that I can think of): 1. a short or 2. a sensor or alarm source that I did not disconnect. If it's a short, why only after I get on plane? What other alarm source is there? I searched for other blue/tan wires and could not find any. If it's an overheat issue, why did alarm not stop when I disconnected the sensor or stop when engine cooled at idle? I've searched for days and not had any luck. Thanks for help

 

[SC_Regal]

Re: Help - Can not figure out alarm

I was not clear - 175 is the normal running temp of my boat

Mike

 

[Fun Times]

Re: Help - Can not figure out alarm

The MEFI-3 engine?s Audio Warning system will sound the alarm differently and it also has additional items that will cause it to sound. If you're ECM checksum number is either D04B or D074, then these additional alarms for your MCM 5.0L EFI engine are turned on within the ecm and will cause it to sound.

The horn will sound if there is an active engine Diagnostic Trouble Code [DTC] that is occurring while the engine is running.

The Horn will sound if the battery voltage to the ECM is low, less than 9v for at least 5 seconds.

The Horn will sound if there is low fuel pressure for at least 5 seconds. These engines have a fuel pressure sensor.

There is what is called a ?soft? and a ?hard? alarm.
1. Soft Alarm = Below 3000 rpm. Horn on for 1 second, off for 3 seconds, on for 1 second, off for 3 seconds, etc.
2. Hard Alarm = Above 3000 rpm. Horn sounds all the time.

 

[SC_Regal]

Re: Help - Can not figure out alarm

Thanks. That gives me hope. I do have a code reader, just need to refresh my knowledge on how to read it. The error code should be stored until I reset - is that correct?

 

[Locke]

SC_Regal

I'm curious what the problem was that caused your alarm, I have a 2000 Mercruiser 7.4 that I put back in the lake yesterday and its doing exactly what yours did. I had the boat out for a transom reseal so the engine was moved around a bit in that process. It runs at low RPM's fine but get up on plane at 3500 RPM and an on-off alarm sounds that will not stop until the engine is shut off. I did unplug the sender at the lube oil reservoir but no change.

I'm going back out tomorrow to try disconnecting the other senders to see if that solves it.

Locke

 

[GA_Boater]

Locke - Please start a new thread. This is over 3 years old and has no fix.