Yanmar 3gm Oil pressure always high

[Hawkg]

I have a 1985 Yanmar 3gmd that has always read high pressure pegged at 80 psi. I had bought the boat like this as the seller told me it was a faulty guage. I have had the boat for 2 years now and use it regularly and have put about 350hrs on it with no problems. It ran for 14hrs straight on delivery. Since buying it I have done complete oil and filter changes every 100hrs. The oil is always black and warm after startup for oil changes.

Several months ago I had replaced the oil pressure gauge and this did not solve the problem. The needle would always be pegged at 80psi even after shutting the engine off.

I recently began tinkering with the oil pressure again and found that if I just turned the ignition key to on without starting the motor the needle would drop to 0 but would instantly peg to 80psi once the motor started and stay after shutting off, even for days.

A few days ago I replaced the oil sender and now the gauge light comes on (didn't do this before) when the key is turned on and psi will start at 0. This told me the sender wasn't grounded previously. However as soon as I start the motor the gauge pegs and stays at 80psi the whole time the engine is on no matter the rpms. The difference now is that th guage drops to 0 along with the tach and temp once the engine is shut off. However the oil pressure needle begins to climb up immediately and stays around 15-20psi and will stay there indefinitely until the motor is turned on and pegs to 80psi. Why would pressure climb to about 20psi and stay there for a whole week?

I am thinking that the oil pressure relief valve is stuck or blocked. Does anyone have any inputs on what the issue may be? I have tried searching for replacement yanmar oil relief valves/switches but I can't find the part anywhere. Is it possible to remove the valve and clean it to remove any debris that's in there? Where can I order yanmar parts like this?

Thank you for your help.

[Uncle Bob]

Originally Posted by Hawkg

I have a 1985 Yanmar 3gmd that has always read high pressure pegged at 80 psi. I had bought the boat like this as the seller told me it was a faulty guage. I have had the boat for 2 years now and use it regularly and have put about 350hrs on it with no problems. It ran for 14hrs straight on delivery. Since buying it I have done complete oil and filter changes every 100hrs. The oil is always black and warm after startup for oil changes.

Several months ago I had replaced the oil pressure gauge and this did not solve the problem. The needle would always be pegged at 80psi even after shutting the engine off.

I recently began tinkering with the oil pressure again and found that if I just turned the ignition key to on without starting the motor the needle would drop to 0 but would instantly peg to 80psi once the motor started and stay after shutting off, even for days.

A few days ago I replaced the oil sender and now the gauge light comes on (didn't do this before) when the key is turned on and psi will start at 0. This told me the sender wasn't grounded previously. However as soon as I start the motor the gauge pegs and stays at 80psi the whole time the engine is on no matter the rpms. The difference now is that th guage drops to 0 along with the tach and temp once the engine is shut off. However the oil pressure needle begins to climb up immediately and stays around 15-20psi and will stay there indefinitely until the motor is turned on and pegs to 80psi. Why would pressure climb to about 20psi and stay there for a whole week?

I am thinking that the oil pressure relief valve is stuck or blocked. Does anyone have any inputs on what the issue may be? I have tried searching for replacement yanmar oil relief valves/switches but I can't find the part anywhere. Is it possible to remove the valve and clean it to remove any debris that's in there? Where can I order yanmar parts like this?

Thank you for your help.

Hi, did you get a matched pair, sender and gauge, or simply replace like for like?

[Hawkg]

I replaced the guage with the same company as the other 2 guages (faria) they are the European guages which I believe to be 180-10ohms. It is 100-250 degree.
The sender was from another company found on ebay and was the only one that was compatible for my engine. I haven't checked the ohms of the sender as I don't have an ohm meter.

[Bill Seal]

You could plumb in a mechanical gauge and eliminate any electrical bugaboos, which you seem to have.

[Orion Jim]

Originally Posted by Bill Seal

You could plumb in a mechanical gauge and eliminate any electrical bugaboos, which you seem to have.

Agree. You have an electrical problem. Anyone handy with a multimeter should be able to track the problem down. Sometimes it pays to spend a few bucks and have a qualified tech tackle a head scratcher.

[Hawkg]

Originally Posted by Orion Jim

Agree. You have an electrical problem. Anyone handy with a multimeter should be able to track the problem down. Sometimes it pays to spend a few bucks and have a qualified tech tackle a head scratcher.

But would that still explain why the psi climbs and stays around 15-20psi after the motor is off and stay? I ran it yesterday for about 1 hr motoring in the harbor, haven't started it today and it is at 15-20psi while the other 2 gauges are 0. I am going to install a new 14awg wire to the sender and gauge tomorrow upsizing from what's currently wired. Also, the way the gauge panel is setup is using the oil pressure positive terminal as the stud to power both the water temp and tach. I was wondering if there is too much current or voltage being sent to the oil gauge to power the other gauges. The negative is setup the same way. The oil guage is used as the bus bar basically. I really don't think this would be an issue however.

[crashley]

Something wrong in the wiring
Oil pressure will be zero very soon after the engine is stopped
Google oil pressure wiring to get a simple diagram
You really need a multi meter to fault find

[Brewgyver]

You're on the right track in replacing the signal wire, from the sender to the gauge. You also need to check all the connections on all the gauges. A bad crimp on either the positive or negative terminal can cause bad readings. If the terminals are not the heat shrink adhesive type, varying degrees of resistance due to corrosion is likely to occur.

Of course, adding a mechanical oil pressure gauge is also a very good idea, and is easily done. Some of the Yanmars have an existing second port on the boss where the sender is attached, if so simply remove the pipe plug and install the tubing connection for the mechanical gauge. If there is no plugged port, you'll have to add a close nipple and tee, or you can order an adapter.

Install the mechanical gauge within your engine compartment, no need to bother snaking tubing to your panel.

[Boatyarddog]

Originally Posted by Hawkg

I have a 1985 Yanmar 3gmd that has always read high pressure pegged at 80 psi. I had bought the boat like this as the seller told me it was a faulty guage. I have had the boat for 2 years now and use it regularly and have put about 350hrs on it with no problems. It ran for 14hrs straight on delivery. Since buying it I have done complete oil and filter changes every 100hrs. The oil is always black and warm after startup for oil changes.

Several months ago I had replaced the oil pressure gauge and this did not solve the problem. The needle would always be pegged at 80psi even after shutting the engine off.

I recently began tinkering with the oil pressure again and found that if I just turned the ignition key to on without starting the motor the needle would drop to 0 but would instantly peg to 80psi once the motor started and stay after shutting off, even for days.

A few days ago I replaced the oil sender and now the gauge light comes on (didn't do this before) when the key is turned on and psi will start at 0. This told me the sender wasn't grounded previously. However as soon as I start the motor the gauge pegs and stays at 80psi the whole time the engine is on no matter the rpms. The difference now is that th guage drops to 0 along with the tach and temp once the engine is shut off. However the oil pressure needle begins to climb up immediately and stays around 15-20psi and will stay there indefinitely until the motor is turned on and pegs to 80psi. Why would pressure climb to about 20psi and stay there for a whole week?

I am thinking that the oil pressure relief valve is stuck or blocked. Does anyone have any inputs on what the issue may be? I have tried searching for replacement yanmar oil relief valves/switches but I can't find the part anywhere. Is it possible to remove the valve and clean it to remove any debris that's in there? Where can I order yanmar parts like this?

Thank you for your help.

Save yourself some confusion and start with a mechanical gauge.
You'll sort it out once you KNOW what the actual mechanical OP is.
Boatyarddog

[Boatyarddog]

Originally Posted by Hawkg

But would that still explain why the psi climbs and stays around 15-20psi after the motor is off and stay? I ran it yesterday for about 1 hr motoring in the harbor, haven't started it today and it is at 15-20psi while the other 2 gauges are 0. I am going to install a new 14awg wire to the sender and gauge tomorrow upsizing from what's currently wired. Also, the way the gauge panel is setup is using the oil pressure positive terminal as the stud to power both the water temp and tach. I was wondering if there is too much current or voltage being sent to the oil gauge to power the other gauges. The negative is setup the same way. The oil guage is used as the bus bar basically. I really don't think this would be an issue however.

Gauge is probably damaged from the "pegging" it.
Disconnect the power to it first, still at 15 or 20?
Replace it.
May need to be match set, OP sender and gauge.
Boatyarddog

[Boatyarddog]

Originally Posted by Hawkg

I replaced the guage with the same company as the other 2 guages (faria) they are the European guages which I believe to be 180-10ohms. It is 100-250 degree.
The sender was from another company found on ebay and was the only one that was compatible for my engine. I haven't checked the ohms of the sender as I don't have an ohm meter.

Faria, is pretty low Quality.
Now Stuart Warner is much better.
https://www.summitracing.com/search/...rder=Ascending
Boatyarddog

[Hawkg]

Thank you for all the replies. I had my neighbor who is a mechanic look at the engine and quickly found out that that the "sender" I had installed was actually a switch and is on-off which always gave the high pressure reading. He told me I'd need to get an adapter with another thread port and Install a real pressure sensor connected to the guage. As for now the switch is hooked up to the buzzer and it buzzes when the engine off and ignition on. I may eventually install a tee adapter and pressure sensor or mechanical guage but will keep it stupid simple for now.