Low oil pressure
 

I get an alrm and my oil press guage drops to zero when i come off plane when running hard for an extended amount of time. This has happened twice .If I run around 3400 to 4000 it doesn't do it. I have check the oil all os good. Not sure what direction to strat to figure this out. Thanks Mitch

Check the wiring to the sender. Something may be loose and move when the boat decelerates.

I did check that doesn't seem to be loose.thanks though

Years ago - this was a straight 6 165hp Mercruiser- it was a VERY HOT Labor Day - I ran this engine for an extended period WOT. I came off plane and the exact same thing happened- oil pressure went to zero, lights flashed etc. I immediately shut the engine down and brought it back to shore. I let the engine cool off-- checked the oil - and it was full - no milk or anything- looked perfect. I restarted and again no oil pressure -- Took it to my mechanic thinking the oil pump may have broke- or worse. When I called the next day - his associate said that he was out on the lake running around. Turns out nothing was wrong with the oil pump, sensor or wiring -- The oil broke down. All they did was change the oil and filter. Up until that episode I was using a straight 30W oil - Rotella -- Never had one bit of problem. Was told that Merc changed and now the recommended was 20-50W. I changed to this weight and never had any issues whatsoever-- Probably put on a good 200 hours after that before I sold the boat.

3pointstar

Cool thanks for the info. I am planning on putting a goof 40w in it when i get home from work in a couple of weeks.

If pressure only drops after running hard how are your oil temps? If oil temps are rising I'd be looking into oil cooler etc..

I dont have an oil temp guage but i will check it and the oil cooler thanks

Get a mechanical oil pressure gauge. Shoot the oil filter after hard run with laser temp gun. It also recommend Mobil one v twin oil. It doesn't break down under high heat load conditions . Just a couple suggestions. Good luck

Thanks for the info. I have been told by several people to try kendall gtx 40w with a fram hp filter.

Is this a new motor ? If so could be bypass sticking open for a few.

It has 350hrs

when you change that oil . cut open the filter n look for signs of bearing material .

I agree with verifying psi thru a mechanical gauge. What oil are you running now?

Im not sure i just bought it from a friend .i believe it may be 20w40 the oil looks good. Bit when i get home from work in a couple of weeks i and going with 40w and good filter. Im thinking maybe changi2out the oil sending unit as well.