Oil Pressure gage getting a reverse signal

I have twin 8.1 Crusaders 2003. I have been having an issue with the port side engine having the oil pressure light and alarm go off and sending the boat into limp mode. There is no issue with the oil pressure. The gage reads 70 PSI. I changed the sensor on both engines and now when I turn the key on the starboard engine the oil pressure gage pins to 80psi. Then when you start the engine the needle goes to zero as soon as you inch the rpm up the alarm goes off and the oil pressure light comes on. I changed the sending unit and still the same thing happens. I am not sure if I fixed the port side issue, but do not know how to find what is happening to the Starboard engine now?

Gauge pinning often the result of a missing/poor ground at the gauge on the dash. Also a bad meter.

Thanks all the ground wires at the helm all look to be good. Not sure what to do next.

Kb1 said:

.... I changed the sensor on both engines and now when I turn the key on the starboard engine the oil pressure gage pins to 80psi....

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If 'sensor' means the sending unit for the gauge, then I'd be tempted to put the original one back in on the starboard side and see if that goes back to 'normal'.

I would also expect that you didn't fix the issue with the port side by changing the oil pressure sending unit for the gauge. That circuit is independent of the ECU...the ECU uses an oil pressure switch to trigger the warning light as well as 'limp mode'. I would suspect that switch is bad; ie it never opens once oil pressure is present.

I changed both on the Starboard side the sending unit and the switch if by switch you mean the sensor which is the piece that looks like an M80 with a single wire connected to it right next to the sending unit. That is what I changed on the port side only. I am working on finding a mechanic with a computer to see if it will tell me what code the ECM is receiving from the engine. I assume low oil pressure?

may be the wire going to the switch and not the switch itself...

Getting the ECU scanned would give you verification you are in the correct area...

Some builders, when installing the engines, will add the 'old style' warning system, as a backup to the ECU based warning scheme...

Just for verification, the sending unit that controls the gauge, and the "switch" that controls "limp mode" are two different units. Make sure you're replacing both, if you're trying to correct a gauge and a "limp mode" situation.