low oil pressure at idle

[Kracken]

Volvo penta 5.0 Gi. The engine has been running fine however when I drop it into neutral. The oil presure drops to 20psi. Normal operation is 40 psi. Oil levels are fine temp is constant at 170. Not sure if I should pull it out of the water and end the (the boating part) of vacation.
Thanks.

 

[Borchik]

Re: low oil pressure at idle

first step would be to put a mechanical guage on the motor and see what it actually is. could very likely be a sender or guage issue.

 

[can-amsledder]

Re: low oil pressure at idle

^^True. ^^

And if I remember right the rule of thumb is 1psi of oil pressure for every 100rpms (at the lowest end of the scale). That seems low but I think that?s what I was taught, been out of school a while. So if you have 20psi at 1000rpms you are double the minimum. Does the oil pressure climb with rpm?
Is it a little higher with a cold motor? Did you change the oil and use thinner oil? (not that it would explain a 20psi drop)

 

[FreeBeeTony]

Re: low oil pressure at idle

Sounds normal to me...........

 

[Gary H NC]

Re: low oil pressure at idle

Sounds normal to me...........

Agree! Seen plenty of boats idle at 20 psi when warm.
As long as it is not rattling or knocking and the pressure rises with an increase in rpm it is nothing to worry about.
Also if you are using a 10w-30 or 40 oil you can switch to a straight 30 or 40 weight and it should come up a little.

 

[Kracken]

Re: low oil pressure at idle

Thanks guys, very, very helpful. I did not want to take a chance on damaging the engine. Yesterday it ran fine. We took a loaded boat for a 2 hour cruise (pressure was fine). After the cruise we took the kids toobin, that's when the pressure dropped. As the RPMs increased, so did the oil pressure. At idle 1000rpm, 20PSI, at 3000rpms 40 psi. The pressure went up with the RPMs

 

[Darringer]

Re: low oil pressure at idle

As oil warms up, it thins out and pressure drops. At idle, even 10psi is enough pressure to adequately lubricate. 40psi under load at normal rpms is plenty. Any more is wasting hp and is unnecessary.