Guys,

I've noticed something a bit odd in the oil pressure in our boat and wanted some guidance on how to think about or deal with it.

Merc 496HO, never been opened up, to my knowledge, so stock internals. It has an M1 ProCharger and a stage 2 Whipple tune, if it matters.

I can run around all day long at idle through cruising speed, and oil pressure stays a reliable 40psi, idle through ~3500RPM or so. But as soon as I stab it and run WOT, or close to it, for any significant length of time, and then drop down to an idle, even after some considerable cruising speed running, the oil pressure drops to ~20psi for awhile, then eventually creeps back up to 40psi over the course of about ten minutes of idling. Oil is fresh, Valvoline high zinc 20W50 Racing oil (last late summer), clear and topped off to the top of the service range on the dipstick.

What do the gurus think might be causing this and is it a cause for real alarm?

Thanks. Brad.

what are you using for an oil cooler? i suspect the oil is getting to hot when running it hard,i like to see oil temp in the 200 to 220 degree range.

As long as you maintain good pressure when running hard your not aerating the oil or it's not draining fast enough back into the pan,,, your good.

Some drop in oil pressure is expected after a hard run. 20lbs is more than enough at idle until it recovers.

Mike,

Whatever came stock with the engine/boat. I don't see anything resembling what I've seen that was called an oil cooler here on OSO. Is there a "stock" one that is integrated into the transom assembly?

Thanks. Brad.

It does in cars, too, unless the gauge is faking it.

Follow the lines off the oil filter housing and you'll find it. With the Pro Charger, it really should be updated over the stock piece (which is quite small).

The stock oil cooler on a 496 is on the port side of the engine above the Cool Fuel housing. It's not very big. Might want to install an oil temp gauge and see where you are at after running hard.

Mine was running 'normal' in a 350 (pair) then after a while at cruise (20 min+) it would drop 20PSI. I removed about 1/2 quart, and now it's dead on. I think it was aerating my oil.

Knot,

I found it. It's farqing buried down there. Will definitely look into installing a temp gauge.

Thanks. Brad.

Just wait until you have to replace spark plugs on that side.