3.7 foamy oil and oil pressure question

[19ft3.7]

My families’ boat has been giving us some strange problems. It is a 1987 165 3.7L. Last summer it had low-pressure 20 psi while cruising and bubbles or foam in the oil. The oil was not milky so we don't think it is water. We put the boat away with new oil for the winter and before we started it this spring we took off the filter Fram and changed it to something better and tapped on the over pressure valve. On the initial run in the driveway the oil went up to 50psi at 2000 rpm seemed to stay up there. We finally got the boat on the lake this weekend and the pressure has now dropped to a little under 30 while cruising and maybe 5 at idle. But the oil is still foamy or has bubbles on the dip stick. We are at the low end of safe on the dipstick so I don't think it is crank whip. Also on start up the engine is noisy but smoothes out. I am assuming that is the oil pressure building up. What should we be looking into about the foam and are we at safe levels on pressure. Can the oil pumps tube get cracks in them and suck air. Any tests that we can do to help figure out our problem would be great. Thanks

 

[Bob_VT]

Re: 3.7 foamy oil and oil pressure question

Anything is possible. I would remove and clean or replace the sending unit if you are that concerned. (the sending units are electirc and not as reliable as a mechanical one)<br /><br />You can also look into having the oils sampled and analyzed.<br /><br />An additional factor is how old is the unit in running time? A 17 year old just might be wearing down a bit.<br /><br />Bob

 

[Buttanic]

Re: 3.7 foamy oil and oil pressure question

Determine proper amount of oil required from specs and put in that amount without reguard to what dip stick shows and see if problem goes away. Could be oil pump pickup tube has broken or fell off or crank whip if for some reason dip stick is not indicating the right level.

 

[19ft3.7]

Re: 3.7 foamy oil and oil pressure question

Engine did not come with hour meter when we got it in 1995 but engine and boat looked brand new. Seems boat dealer may have taken it off because of low hours and moved it to anouther boat it looked like there was spot for it. We might put 40 hours on in a year if that. So engine probably has 600 to 800 hours. Engine seems to be running great. To change the oil we pump through the dip stick. It usally takes 5 of the 6 qts specified when filled to almost full on the dip stick. I am afraid with the foaming oil we will burn some bearings up. Oil anylsis is probably a good idea. I am afraid it might be the pickup tube. Any way to check it without pulling the motor?

 

[Buttanic]

Re: 3.7 foamy oil and oil pressure question

I wouldn't run it until the problem is solved. The engine will have to come out to check the pickup. I dought there is enough room to remove the oil pan with the engine in place.

 

[Buttanic]

Re: 3.7 foamy oil and oil pressure question

Looking at the parts breakdown drawing the pickup is bolted to the pump with an O ring to seal it. The bolt could have losened and/or the O ring failed. At high RPM more oil is up in the top engine than when idling so the level in the pan is lower and if the O ring is bad or the bolt is lose the oil level could drop low enough to suck air. I had a 283 Chevy that the pickup fell off and at idle the oil pressure was normal but at high speed it would drop because of the lower level in the pan.