Mercruiser 5.7 temp/oil pressure norms

[njmedic3306]

This is my first I/O so bear with me.

The motor seems to run nice and cool, around 160 when I am above idle. When I run it real slow in no wake zones she starts to warm up to about 180 and she idles about 500rpm. Is this normal because the impeller is turning so slow? Even the oil pressure guage drops to about 20psi.

 

[Turn-n-Burn]

Re: Mercruiser 5.7 temp/oil pressure norms

I tried the search function for the specs on iboats.......sorry....had to resort to google.....

http://www.perfprotech.com/store/articles/mercruiser-v8-engine-specifications.aspx

 

[Aloysius]

Re: Mercruiser 5.7 temp/oil pressure norms

10# pressure per thousand rpms is acceptable..most oil lights turn on 3-7 #'s of pressure. 500 rpm idle is a little low.

 

[Fireman431]

Re: Mercruiser 5.7 temp/oil pressure norms

You didn't give any indication of whether is was carb'ed, EFI, etc.

As low as 20 psi when up to temp isn't unreasonable, depending on the weight of the oil and the age.

Temps are fine too. Gets a little warmer at idle because it's not moving as much new cool water.

 

[NHGuy]

Re: Mercruiser 5.7 temp/oil pressure norms

Agreed, temp & oil pressure are fine. Idle fully warmed up, in gear my carbed 5.7 calls for 650 rpm, if your boat isn't fuel injected you may want to adjust it to 600 or 650 rpm at idle. It might hold that 160 temp a little longer with the extra rpms.