496 Mag Oil Pressure question....

[WickedRx]

496 Mag Oil Pressure question. I have a 2009 350/370DA with twin 496s at about 650 hours each. They run fine and have new oil changed this past spring using Mercruiser synthetic and are both full. At idle, the There is an oil pressure difference of about 0.2 psi, however at slow cruise (8-10 mph) that difference increases to about 1psi, with one engine putting out about 5psi and the other around 4psi. On a relative sense, this is a substantial difference, but on an absolute sense, not sure if 1psi at cruise matters. There are no alarms or anything going off. Recently had a mechanic replace water pump and one of the pulleys on the engine with lower oil pressure, not sure if belt tension may have a role in this situation or not. I welcome thoughts or feedback. If it's not an issue, I won't worry, but oil and temp are those types of things that gets me on edge. Thank you.

[Brite_Idea]

8-10 mph equates to how many RPM? I'm thinking that in reality you're gauges are transmitting what the sensors are telling them. The problem is a mechanical gauge would be more reliable. I wonder has the pressure always been 5 psi at 8-10mph or is this a new development? If it were my boat I'd buy a mechanical gauge and do some tests to verify accuracy of the digital crap. I'll bet you'll be ok but find out that the digital readings are lower than reality.

[WickedRx]

Thanks @Robert Breit. 8-10mph on our boat is approximately 1650 RPM. I did manage to speak to our mechanic who suggested the reading differences are not worrisome. Likely something akin to what you suggested, minor differences in digital readout or something. As far as the history of the problem, I do not recall noticing it until a few months ago, but that could be my inattention, or because there are no alarms associated with it, that I ignored the differences.

[Steppenout]

4-5 psi is not acceptable oil pressure at any speed. It sounds like it may be an issue with the electronics. A good mechanic would hook up a mechanical analogue gauge and verify that the actual oil pressure is within specifications.