Merc v150 oil alarm

[kmcampbell]

1999 Merc V150. After running about 20 minutes I got an oil alarm and the engine started to power down so I shut it off. The oil tank and reservoir were full and the pickup filter was clean so I went back to the dock on one engine.

One at a time I swapped out the warning module, oil pump, oil cap and motion sensor from one engine to the other and started the engine after replacing each part. All works fine on the port engine but I'm still getting the alarm on the starboard engine. The oil pump gear appears to be in good shape. No plastic shavings present. The alarm comes on within seconds of starting the engine.

With the pump disconnected I turned the drive and its pumping oil out. I reinstalled the pump and started the engine and observed about 3 drops of oil pumped out in about 10 seconds.

I disconnected the motion sensor wires and started the engine without an alarm. Once I reconnected the sensor the alarm started. I ran the engine with the sensor out of the hole with all the wires connected and no alarm until I physically put the sensor back in the hole. Both motion sensors work fine on the port engine.

I also switched the two audible alarms and same problem. With the cap off the reservoir began filling up as it should and I placed the cap back on tightly.

Is there anything else that causes this alarm to trip?
Is it a ground issue and if so how do I track that down?
Should I try switching the reservoir tanks?

I would really appreciate any help that anyone can offer as I'm at my wits end.

Keith

 

[rodbolt]

Re: Merc v150 oil alarm

I suggest you carefully read the service manual.
there is no power down or speed limiting function on your merc
if it was powering down it was dying.
the oil alarm is a beep beep thing and the overheat is a steady tone.
a bad switchbox can also toggle the alarm. test your switchbox output or move the green wire from the alarm module to another switchbox terminal.
the service manual has some very specific details but it doesnt really cover the motion sensor and how it works.
if the sensor gives the module a signal and the switchbox does not it will trigger the alarm.
a bad stator or trigger can cause the oil alarm to trigger as well.
but do run it on a premixed tank while testing just in case its an actual oil system failure.
the remote tank contains NO alarm or warning functions so dont go there.

 

[j_martin]

Re: Merc v150 oil alarm

I'm with RodBolt. An ignition failure will make the engine spool down and also trigger the oil alarm.

To help out, I'll explain briefly how the oil alarm works. When you power on, it does a self test, and beeps a few times. It looks at a switch in the engine oil resevoir that is supposed to close if the oil level starts to go down. If that switch closes, the alarm goes off. It also looks at a pulse from a sensor in the oil pump and at the same time looks at a sample ignition pulse from the switchbox. If pulses are missing at both places (engine stopped), all is good. If pulses are coming from both places (engine running), all is good. If either pulse is missing while the other is there, the alarm goes off.

I suspect the ignition pulse is missing.

Hope it helps
John

 

[kmcampbell]

Re: Merc v150 oil alarm

I switched the green alarm module wire to a different terminal and same issue. I switched it to the inside switch box and no oil alarm, but suspect my switch box might be failing. I will take the boat out this weekend to see if I'm having any other problems. Thanks for the great advice.