Oil pressure gauges

"Just picked up 1990 272 Formu

"Just picked up 1990 272 Formula.Its equipped with twin 502 mag EFI Mercruisers.[I think they are 94s]. When starting the motors cold,the oil pressure gauges reads 20-30 lbs, raising the RPMs, pressure drops.They read about 30 -40 when running the boat.Then they will read 60-80 lbs at an idle. It almost seems like the gauges are reading backwards.These motors are not the original motors.They were swapped out for 454 which came with the boat new.All of the gauges seem to be giving false readings.Maybe the wiring harness are different."

"If they are both acting the s

"If they are both acting the same way it's possible the resistance (ohms) of the senders don't match the guages, check the back of the guage to see if there is a range ie: o psi = 240 ohms, 80 psi=33 ohms or something like that and then you can measure the senders both when the engine is cold and when it's running or you could pick up a mechanical oil pressure guage and remove your sender and intall the guage, only problem is you have to be at the engine see what it's reading."

"I agree with Bob on the sendi

"I agree with Bob on the sending uint being incorrect for the gauge or something alone those lines, but I also feel it is best no matter what it takes to have the pressure checked with a mechanical guage.

An automotive type rubber brake hose is great for extending a guage out enough that it can be read while runnig the boat.

Hope it is nothing more than the sending unit."

"Thanks fellows,The problem wa

"Thanks fellows,The problem was the mismatch of the sender with the gauges.The boat is equipped with VDO gauges and they do need to be matched up with VDO senders.Obviously when the motors were swapped they didnt bother to change the senders.Ill check the other guauges to make sure they are accurate too.Thanks"