We have a 2000 Checkmate 259 Convincor powered by a stock 454MAG. The boat has logged 189 hours. This year I have noticed the oil pressure gauge find itself in the L speckled paint side of the gauge at idle after a hard run. Is this something to be concerned about? When the engine is cold oil pressure is strong at idle. The only time the oil pressure drops is after running the boat for an extended period of time at or above 4000RPM and then idling. Could the oil in the boat be the wrong viscosity? Oil level is good and clean. Any thoughts would be appreciated.

Several things are happening. Your oil is getting hot and thin, and possibly foaming. After a long run your oil will get a little air entrained and will show lower on the gauge. Probably why it hasn't appeared in past years is because your engine bearings have a little more clearance than before. As long as you have decent oil pressure while at speed, this shouldn't be a problem. Do you have an oil temp gauge too?

what oil are you running ???????

10psi for every 1000rpm is ok!(when warm)

I am not sure. We have a marine mechanic winterize the boat once a year. I will ask him.

Our oil pressure gauge has L to the left and H to the right with speckled paint close to the L. No numbers on the gauge at all. Maybe I should buy better gauges.

No oil temp gauge. Thanks for the insight.

also kind of sounds like someone may have installed a multi visc oil... if so .. change to a straight weight.

Don

I have noticed the same on my boat, 454 running the merc multi viscosity mercruser oil. I don't think merc sells a straight weight, at least i haven't seen it.

ALL of my boats have done this after a long, hard run. If it didn't do it before they may have used a lighter weight oil when they winterized.