Raylar

Paul:

Stock oil pressure on 496's with a good 20-50W weight oil on a cold engine will run about 35-45 psi cold and can be as low as 30psi warm at idle, with higher rpm oil pressure at about 45-55 psi cold and about 40-50 psi warm after running at loads. An oil pressure under 30psi at idle or under 40psi at high rpms usually indicates a possible problem with oil weight, oil pump or internal engine issues like bearings and such. The Mercury 'Guardian" alarm feature should sound if the engine goes below 20psi and the power will be reduced significantly to help protect the engine at that point. Also do not overfill the crankscase as this can cause oil foaming and pressure loss from that condition.

Best Regards,
Ray @ Raylar

Best Regards,
Ray @ Raylar

Rage

The Mercrusier tech line said that the oil pressure when the Guardian system will respond to protect the engine is 8-9 psi regardless of rpm. I have personally been as low as 10-12 psi oil pressure at idle and the Guradian did not kick in.

paul buckner

thanks Raylar ,ran motors up today all new oil and filters all seems well 40 psi at idle reved it to 2500 went up to 45 psi they both sound sweet they look as good as new only 142 hours .the only reasen i was worried is iam going to buy a coulple of master lubes to pre lube the motors befor start up and the guy said he thought that the 496 ho motors ran 80 but i thingk he was gessing psi thanks again Raylar i will let you no how it runs soon as i take tit out REGARDS paul from uk

paul buckner

just noticed that the oil merc sent me for the 496ho is 25/40 bu t Raylar say a good 20/50 should i go 20 /50 next oil change regards paul

Raylar

Merc 25-40 oil is just fine, its just a little expensive for what it is.
Rage, did someone reprogram your ecm, cuase it sounds like your guardian system features on that input may be turned off and thats a little dangerous. Most every time I've seen or heard of the oil pressure on a Merc 496 go under 20 psi, the guardian kicks in.

Best Regards,
Ray @ Raylar