Oil Pressure drops and sets off alarm

[ardeprint]

Hello,

Lately I have been experiencing a new issue. My oil pressure gets very low after a good run. As soon as I get down to idle the oil pressure guage drops to, what looks like, 5psi and a steady alarm goes off. Engine will cut out, but not turn off, but it will not rev up. As soon as I turn engine off and turn it back on alarm goes away and engine runs fine. Oil pressure steadily starts to go up as the engine settles or cools off.

Now, I obviously have a problem, but I would like some advice as to how I should tackle this. I have heard it all from the good to the bad. I've been told it could be as simple as a sending unit. Also, the dreaded the engine is worn out and thats why pressure is low. At cruising the oil pressure is good.

What, other than a bad oil pump, would couse low oil pressure? Is a low oil pressure a sign of a worn out engine?

 

[33ec]

as you know, any number of things can cause this. I would suggest you start with the simple things. sending unit is a cheap and easy swap. I would start with an oil change-how old is the oil and is it diluted with fuel. thinned out oil will cause the conditions you describe and it would be worth pulling a sample for testing before major engine surgery. the oil sample will guide you in the right direction and you might get lucky and discover a simple fix such as a leaky injector or some other source of dilute/thinned oil.

doug

 

[ardeprint]

Good advice! I agree!

Engine oil is new and injectors have recently been serviced with good pre and post results.

I did start using Racor oil filters instead of the Quicksilvers. I'm not sure if this is coincidence, but I THINK, it started when I did that. Maybe I'm just being optimistic, but will start with a new oil filter. Then a new sending unit. And, finally an oil change to a higher oil weight like straight 30w rather than the recommended 20-50w. If better results are achived with higher weight oil then I guess, I do have a worn out engine cituation.

 

[Wylie_Tunes]

I would first double check the oil level while the boat is floating, as opposed to being on a trailer for a smaller boat. Too low can cause an oil pressure drop, but so can too high. If the level is too high, the oil can foam up in the crank case. The oil is basically aerated and the foam will cause low pressure.


next, smell the oil for a gas smell. A rich running engine will result in oil dilution. This thins the oil, thus causing lower pressure as well as increased wear.


Another possibility would be that the oil drain back holes in the head are restricted. This allows the oil to pool in the valve covers. It gets to a point where the level in the pan is low. This ones hard to detect without pulling the valve covers, but once you do, you will know.

 

[ardeprint]

I would first double check the oil level while the boat is floating, as opposed to being on a trailer for a smaller boat. Too low can cause an oil pressure drop, but so can too high. If the level is too high, the oil can foam up in the crank case. The oil is basically aerated and the foam will cause low pressure.


next, smell the oil for a gas smell. A rich running engine will result in oil dilution. This thins the oil, thus causing lower pressure as well as increased wear.


Another possibility would be that the oil drain back holes in the head are restricted. This allows the oil to pool in the valve covers. It gets to a point where the level in the pan is low. This ones hard to detect without pulling the valve covers, but once you do, you will know.

Thanks for input!
New heads, so not likely the problem. Boat is always on (in) the water. You bring up a good point when you say "running rich" I have been running rich lately, but have corrected the problem. Will check oil smell.

On a related note, I am thinking of having the oil inspected. Anyone know a good oil testing facility?

 

[carterchapman]

Rather than just checking the oil "smell". get a free Blackstone oil sample kit, send it off to them for a full analysis - $25.00.

http://www.blackstone-labs.com/

 

[ardeprint]

Rather than just checking the oil "smell". get a free Blackstone oil sample kit, send it off to them for a full analysis - $25.00.

http://www.blackstone-labs.com/

Thanks will contact them now.

 

[carterchapman]

I have them do my engines/trannys/genny on my 340 each year prior to fluid changes...

 

[ardeprint]

Just read that a PCV could contribute to a low oil pressure reading after a hard run. Any thoughts or experiences?

 

[GrandMaster]

Good advice! I agree!

Engine oil is new and injectors have recently been serviced with good pre and post results.

I did start using Racor oil filters instead of the Quicksilvers. I'm not sure if this is coincidence, but I THINK, it started when I did that. Maybe I'm just being optimistic, but will start with a new oil filter. Then a new sending unit. And, finally an oil change to a higher oil weight like straight 30w rather than the recommended 20-50w. If better results are achived with higher weight oil then I guess, I do have a worn out engine cituation.

Different oil filters can be designed to work at different oil pressures so it is very possible that this is your problem. If I remember correctly there was another thread about someone with a similar problem and once they went back to the Merc-approved filters the problem went away.

 

[ardeprint]

Different oil filters can be designed to work at different oil pressures so it is very possible that this is your problem. If I remember correctly there was another thread about someone with a similar problem and once they went back to the Merc-approved filters the problem went away.

I hope!!! Thanks for you input.