Dropping oil pressure

[Ovmman]

Hey guys, I have twin 2005 4.3s. Upon start up, both have about 55 psi oil pressure. After about 15 minutes cruising at 3500, port oil pressure drops to about 35. At idle, it will drop to about 20. Starboard will stay at 55 and drop to 30 at idle. Any ideas as to what would cause the drop in pressure on the one motor? On changing the oil, the oil does seem lighter in color, but can find no evidence of water in oil. Oil level remains the same. Might use a quart of oil over the season. This has been going on for about 2 years now. I will change the sensor. Is there one sensor for both smart craft and analog gauges? What would be your next step? Thanks guys. Tony

 

[blaster]

What viscosity oil are you using? Have you confirmed the oil pressure with a mechanical gauge? 30 psi at idle isn’t low at all. I believe the minimum at idle is 6 psi.

You could swap the sensors and see if the readings change.

 

[becnme]

I would not worry, you are within specs. Does one engine have a remote oil filter and not the other?

 

[Lazy Daze]

If it's been that way for two years, I wouldn't worry about it - focus on other things. You are WELL within specs. The more important thing is to watch for trends - not so much actual numbers.

 

[Ovmman]

Thanks for the responses. I have been using mercruiser 20 W50. Curious why it would drop. Boat sits in saltwater with 300 hours on it. Thanks Tony

 

[Lazy Daze]

Thanks for the responses. I have been using mercruiser 20 W50. Curious why it would drop. Boat sits in saltwater with 300 hours on it. Thanks Tony

Because the oil warms up. Totally normal.