Overheat/low pressure warning

[bashr52]

I'm trying to work out the bugs on my new boat, it has a 1994 4.3L Mercruiser and alpha 2 outdrive. There is supposed to be an alarm that goes off if the temp gets to high or oil pressure drops to low. The decal says to leave the key in the on position for 7-14 seconds until the alarm goes off in order to test it. I tried this and there is nothing going off. I want to make sure this is working as its kind of important.

How does this work and what should I look for to get this fixed?

Also, neither the trim gauge or speedometer appear to be working either....

 

[spoilsofwar]

First step should be to locate and test your alarm buzzer. Usually they will be tucked up under the helm somewhere.

Sometimes, unwise people disable them so they can continue to ignore overtemp issues (!) You're smart to want it working.

I'm not familiar with Merc I/O stuff, but at least on my Volvo, the alarm will sound as soon as the key is placed in the "run" position and until the engine is started (since it is seeing no oil pressure). Sounds like yours is similar but with a delay involved.

 

[Bondo]

There is supposed to be an alarm that goes off if the temp gets to high or oil pressure drops to low.

Ayuh,.... Welcome Aboard,..... There oughta be 3 switches that trigger the alarm,....

One in the T-stat housin' for the temp,....
One either by the distributor, or down low portside of the block, for low oil pressure,....
'n one on the drive's oil bottle to tell ya it's low,....

To test each, pull the wire off the switch, 'n ground it,... The alarm should sound when grounded,....

The trim sender wires usually rot off at the switch on the gimbel ring,...

The speedo might be unhooked, or the hole in the front of the drive is plugged,....

 

[alldodge]

Agree, and as spoils mentioned some disable them (bad move). Basically when the key is turned to ON, 12V is applied to the purple wire behind the helm to the motor and gauges. The same purple wire also applies power to one side of the alarm beeper. The beeper in most cases is black, round and slightly larger then a quarter, and about 1/2 inch thick.

The other side of the beeper feeds all the sensors listed by others in this thread. When one of the sensors grounds it turn on the alarm. The 4 to 15 second delay is incase it has a capacitor installed. My 1995 Rinker sounds off as soon as the key is turned to ON, there is no capacitor.

So find the beeper and check to see if 12V is still being applied.