Universal M25XP Oil Pressure Sender

[Shadowfax]

I have a Universal M 25 XP engine. I started the boat this weekend to find that the alarm buzzer for the oil pressure is not working. Changed out the buzzer but still nothing, so I'm suspecting the oil pressure sending unit. Looked around but couldn't find it. I suspect it's hidden somewhere under the starter or some other fun spot impossible to get at.

Does anyone know where exactly it is?

Thanks

 

[Rocinante33]

Paul,

On my M25 it is mounted on the top of the bellhousing, aft of the cylinder head. The M25XP is probably the same.

 

[Tom Metzger]

Oil pressure switch

Port side aft below the manifold. Go in from the side access hatch by the aft cabin. Follow the light blue wire (probably painted).

 

[newgringo]

On our 1985 M25 the oil sender switch is located just above the starter motor under the exhaust manifold. It screws into the block and you will probably need a special 1 1/16 inch socket wrench which you can get at NAPA to R&R it (I did). The switch should be normally closed at pressures below 5 psi. I just installed a new one I got from Kubota PN 15841-39010 for $11.81. Good luck.

 

[Shadowfax]

Thanks

Thanks all, I hope it nothing more then a loose wire, but that never happens.

 

[Tom Metzger]

Paul - Touch the lead to a ground; the alarm should stop. You can do it at the switch (sender) and again at the buzzer if the first test didn't work.

The switches are pretty much generic so you don't need a Universal or Kubota part.

 

[Shadowfax]

Tom,

It's not that it won't stop, it won't come on. I've got my son down there at the the moment trying to trace down the wire to the sending unit to make sure the wire didn't come loose or something of that nature.

 

[newgringo]

Fwiw

On our M25 the alarm sounds when the oil pressure sender sees less than 5 psi which closes the switch, grounding the circuit. Understand others may be different.

 

[Tom Metzger]

Paul - Disconnect the wire and it should sound off.

 

[Shadowfax]

Tom,

If I disconnect the wire and it doesn't sound off does that mean the the switch is bad? The buzzer is brand new.

 

[Tom Metzger]

Paul - No, I mis-spoke. The wire must be grounded to sound the alarm. The switch is normally closed when the engine is off - no pressure. Sorry about the confusion.

Testing the Oil Pressure Gauge

• Test the gauge by grounding the wire that leads to the sending unit on the block.
• When the wire is grounded with the key switch on, the gauge should show maximum oil pressure, or the light should go on.

If the switch reads low resistance with engine off it is bad.