Mercruiser 165 1987

[Rob McGinn]

Last year I bought a used 1987 cres Phantom 185, from a friend's father in law. I am mostly using it for trolling but when the engine has heated up the idling oil pressure is zero. I have to go to about 500 revs before some modest oil pressure starts to show. I was told by a mechanic to try replacing the sender which did nothing to solve the lack of lubrication problem. A trusted mechanic and friend told me that the engine probably needs a serious rebuild or replacement!! When I take the boat out I will take it to him for an assessment.....Leak down test etc . I am really wondering if it is worth the bucks to replace the engine with a rebuild

 

[Bt Doctur]

The engine should not get much above 140-145 degrees at any time and the oil should be 25W-40
The oil could be diluted by gasoline entering the cranklcase

 

[nola mike]

I'd verify that with a mechanical gauge and sender--you wouldn't be lasting long at 0 psi. Wait, you said no pressure below 500 revs? You shouldn't ever be getting that low...

 

[Alumarine]

Somethings not right.
Your tach must be off as the motor really won't run below 500 rpm.
Try a different tach and a manual oil pressure gauge to see what's really happening.
If you had 0 oil pressure you'd have some clacking I think.

Is this an inline 4 cylinder or inline 6 cylinder 165?

 

[stonyloam]

The engine should not get much above 140-145 degrees at any time and the oil should be 25W-40
The oil could be diluted by gasoline entering the cranklcase

87 that would be a 470, so it should run about 160-170 F. Agree, change the oil, I use Rotella 15w 40, in either case you want a heavy duty oil, what I use in my diesel tractors and combine.