Oil Pressure

[Cadan]

I took the boat out this weekend and have a problem with the oil pressure. At tick over and towing speed 20 - 25mph the oil pressure is normal. However when i push it the pressure drops into the red on the gauge. The engine has only 140 hours on it so im hoping its not the oil pump. I am going to try an oil change, just in case the previous owner has put the incorrect oil in. Has any one experienced this problem before and can any one tell me the best oil to use. The engine is a Mercruiser 350 MAG tow sport.

Any comments very welcome

[rossl]

When you say, just in case the previous owner has put the incorrect oil in, does that mean this is the first time you have run the boat?

For reference: our boat ticks over @ 40psi and goes to 60psi while running if it went below 20psi or red i'd stop running it. Make sure the oil is topped up, oil cap is tight on and not cracked and dip stick is fully in also.

Cheers
rossl

[Tower_boy]

Hmm... have you checked the oil recently? Could be as simple as a top up required.

Mike

[saltwater_cowboy]

When you say drops into the red do you mean extremely low or high? Both are not good.

Oil pressure is always higher when started from cold. It should be in the middle to 3rd quarter of the guage when cold and anything from 2nd quarter to middle when warm.

If its dropping to low pressure when warm it could mean it needs topping up and/or the incorret grade oil has been added. Most GM engines call for SAE30.

[Cadan]

I bought it in November but only run it a few times as there were a few other issues, the pressure drops to around 10 psi at speeds greater than 25mph but below this speed sits normal at 40 psi. I must admit i didnt notice it before the alarm went off. I checked the oil level, it was within the tolerance level, if a little on the low side. I am hoping it is not the oil pump as i believe it is an engine out job.

[bigben]

Hi all - my first posting on these forums. I've been working one getting a rebuilt 350 Mag Ski into a 1993 Ski Supreme, planning on showing a few pics of the progress soon - will post a proper introduction in the next few days lake, boat etc - in the meantime here's a little pic of the engine - 350 Mag

Anyway back to the point - the Mercruiser Quicksilver Oil is 25w40 so something close to that should be used - (I'm planning on 20w40 as it's easier to get hold of for me)

It does sound like you haven't got enough oil in the sump or the oil is too thick and not running back into the sump quickly enough at high revs.

Could also be sludge build up blocking the oil pick up strainer - I'd try a new oil filter and an oil change to start with.

There is a trick I learned from a VW forum, if you put 500ml of Automatic Transmission Fluid (cheapest you can find - any brand) into the engine oil and run it GENTLY for 30 mins or so before the oil change - it really helps clear out all sludge and varnish kicking around in your engine.

This does have to come with a health warning and I can't accept responsibility if the engine, develops oil leaks (good chance if sludge is blocking up holes), falls to bits, blows up, etc, etc.

Anyway - I hope this helps !