My 36 MK 1 with the Universal M25 XP has just begun to sound the alarm at the switch panel when the engine is running. There is no oil pressure gauge at the panel, and no oil pressure idiot light. Since the coolant temperature is normal, I am assuming that this alarm is from the oil pressure circuit. The engine oil level is at full, and the engine sounds and runs normally. I disconnected the blue wire to the oil pressure switch in the block with no effect. Today I replaced the oil pressure alarm switch, again with no effect. I read on the forum that a failed resistor can cause this, but that resistor was apparently added to the circuit 10 years after my boat was built.
Any thoughts on what is causing this, and where to go from here? Thanks
Oil pressure alarm sounds continuously
Sat, 05/24/2025 - 15:17
#1
Oil pressure alarm sounds continuously
I had that problem and it took one year to figure it out.
as a first step remove the 2 wires from the oil pressure switch and connect them to each other. The engine does not have to be running. If the beeping stops then you have a bad switch or it is the wrong type as in normally open or normally connected contacts. It shoukd be normally closed contacts on the switch.
You indicated the beeping is continuously on. This is due to faulty high temperature sensor located on the top of the engine above the thermostat. Disconnect this wire and see if it stops the beeper.
In my case it was due to excessive engine vibration which vibrated the high temperature sensor bymetal switch producing a false signal. The engine vibration was due to cracked alternator bracket which made the alternator swing and shake the engine.
Check the alternator bracket.
Sail La Vie 1999 Catalina 36 MKII,(link is external) M35B-17031, Coyote Point, San Mateo, CA (link is external)
About Sail La Vie(link is external)
Thanks for the reply. There is only one wire coming from the oil pressure alarm switch; I think if there are two wires, one goes to the fuel pump shut-off in newer versions of the boat. Disconnecting the one wire I do have does not shut off the audible alarm, and grounding it to the block has no effect either. Disconnecting the wire from the thermostat only turned off the coolant temperature gauge at the instrument panel.
I bought an oil pressure testing kit and screwed it into the block this morning; oil pressure on cold engine idle is 55 PSI, so the oil pressure is good. I'm tempted to take the audible alarm out of the circuit and install an oil pressure gauge in the instrument panel. I'd like to have an alarm, but the one that I have already has such low volume that I can't hear it when the engine is running unless I stick my head into the port cockpit locker, so I wouldn't be much worse off. I suppose I could replace the alarm itself with a louder version but then I think I'd need a T fitting at the oil pressure port on the block to run both the gauge and an alarm.
There are two sensors for the water temperature. One is connected to the guage to indicate water temperature, but the other sound the alarm indicating unacceptabley high temperature. This is the one that gives trouble.
Sail La Vie 1999 Catalina 36 MKII,(link is external) M35B-17031, Coyote Point, San Mateo, CA (link is external)
About Sail La Vie(link is external)
My 2 cents worth. I'll bet you have original alarm which has a small circuit board attached to it. Several years ago my alarm was going off at a very low level while running. It was intermittent. I believe I changed the sensor in the block but still the issue remained. I bought the new alarm I believe from CD and installed, problem gone. Alarm is very loud and you won't have any issue with hearing it.
Gary Bain
S/V "Gone With The Wind"
Catalina 36', Hull #: 1056, Year: 1990, Engine: M-35
Standard Rig
Moored: Boothbay Harbor, Maine
Home: Auburn, Maine