Oil Pressure and Water Temp Alarm Test

[crepko]

Is there an easy way to test if the audible alarm is working on a Mercruiser 5.0 if the temp gets too high or the oil pressure too low. Previous owner of this boat blew a head gasket when he overheated the engine. Didnt get a chance to ask him if the alarm went off of not before he damaged the heads.

Boat: 2007 Chapparal
Engine 5.0 Mercruiser Carburated
Engine: OW613721
Transom: OW437012
Drive: OW841226

 

[Bt Doctur]

Failure to watch the gauges will do that.Only test is grounding the alarm wire at each sender to see if the buzzer goes off

 

[isaacs]

You'll know if your oil pressure alarm is not working. As soon as you switch your ignition switch to the on position your buzzer should sound and will continue to squeal 'till the engine builds up some oil pressure.

If you get no squeal when you turn on your ignition, try shorting the temp switch and the lower unit oil reservoir to ground while your ignition is on, engine not running. If these set off the alarm, then your oil pressure switch or the wiring going to it is bad. I had to replace mine; it's hard to find but easy to change.

 

[crepko]

Failure to watch the gauges will do that.Only test is grounding the alarm wire at each sender to see if the buzzer goes off

We did the test this weekend. Using an alligator clip wire to a good engine ground we grounded the wire that attaches to the oil pressure sender. The audible alarm went off. We did the same test grounding the wire to the water temp sensor next to the thermostat. It has a tan wire. No alarm sounded. we attempted this several time while the engine was running. No alarm sounded.

Later in the evening however we accidentally discovered the high temp alarm is actually working. We were doing a test of the impeller with the stern drive lowered into a 44 gallon bin of water. The impeller was working fine for about 8 minutes but then the water in the bin got to low and the impeller started pulling air. The engine temp rose to 190 ish and the alarm went off. We killed it immediately when we heard the alarm. We later discovered a crack in our bin and we were losing water faster than we were filling the bin.

So in summary the ground test did not work to test the alarm (Tried 5 or 6 times at different ground points). But the alarm clearly works. So maybe the test is flawed or could I be missing something? Maybe there is more than one temp sensor?

 

[isaacs]

We did the test this weekend. Using an alligator clip wire to a good engine ground we grounded the wire that attaches to the oil pressure sender. The audible alarm went off. We did the same test grounding the wire to the water temp sensor next to the thermostat. It has a tan wire. No alarm sounded. we attempted this several time while the engine was running. No alarm sounded.

Later in the evening however we accidentally discovered the high temp alarm is actually working. We were doing a test of the impeller with the stern drive lowered into a 44 gallon bin of water. The impeller was working fine for about 8 minutes but then the water in the bin got to low and the impeller started pulling air. The engine temp rose to 190 ish and the alarm went off. We killed it immediately when we heard the alarm. We later discovered a crack in our bin and we were losing water faster than we were filling the bin.

So in summary the ground test did not work to test the alarm (Tried 5 or 6 times at different ground points). But the alarm clearly works. So maybe the test is flawed or could I be missing something? Maybe there is more than one temp sensor?

There should be two temperature sensors. One is a sender that controls the guage on the dash. The other is a switch that controls the alarm. I have a feeling you were grounding the wrong one.