Merc 5.7 normal oil pressure @ 3200 rpm's?

danond

Lieutenant Junior Grade
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Jun 11, 2007
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Re: Merc 5.7 normal oil pressure @ 3200 rpm's?

Why what is yours?

It changes with engine temp and age/wear. My 4.3 runs around 40-45 psi (based on my crappy factory gauge) when it's warm at that RPM.
 

swordfish25

Petty Officer 2nd Class
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Mar 18, 2009
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117
Re: Merc 5.7 normal oil pressure @ 3200 rpm's?

Yuo can not get a good reading with those eletc. gauges. Check it with a mechanical oue, and go from there. 25 to 30 idleing is good. Us 30 weight oil.
 

JustJason

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Re: Merc 5.7 normal oil pressure @ 3200 rpm's?

general rule of thumb is 10 psi for every 1000 rpms. Some will always be a little more or less depeding on wear, age and weight of oil etc.

BTW... the engine only needs a couple of psi at idle.
 

Mark L

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May 31, 2009
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Re: Merc 5.7 normal oil pressure @ 3200 rpm's?

on my crapy meter it looks 40 at idel then goes up 60 psi at 3200
I don't know if its an issue? motor sounds ok and boat and boat runs around 20 knots with out pushing to hard temp looks ok
just not sure?
 

JustJason

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Re: Merc 5.7 normal oil pressure @ 3200 rpm's?

if it sounds fine, and runs fine, then it's probably..................
 

Mkos1980

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Re: Merc 5.7 normal oil pressure @ 3200 rpm's?

It'll always go higher with more RPM's. Your turning the oil pump faster...
 

Polar_Bus

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Sep 6, 2008
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Re: Merc 5.7 normal oil pressure @ 3200 rpm's?

BTW... the engine only needs a couple of psi at idle.

Any GM based engine with "with only a couple od psi at idle" is a questionable set of main and/or rod bearings and will spit a rod at any time. GM oil pressure warning lights will usually trip off at anything under 7 psi.

A GM engine with a "tight" bottom end should put out around 35-45 psi idleing or otherwise (with a standard volume/pressure type pump).
 

Polar_Bus

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Re: Merc 5.7 normal oil pressure @ 3200 rpm's?

It'll always go higher with more RPM's. Your turning the oil pump faster...

GM oil filter adapters have a built in bypass pressure system, They typically only filter approx 60% of the oil. This is so when your oil filter gets excessively dirty (creating added pressure) you don't burst the filter canister.
 

Mkos1980

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Re: Merc 5.7 normal oil pressure @ 3200 rpm's?

GM oil pumps have a built in bypass pressure system, They typically only filter approx 60% of the oil. This is so when your oil filter gets excessively dirty (creating added pressure) you don't burst the filter canister.


HUH? The spring in the pump is just there to bleed off pressure when cold or high RPM's. Your thinking of the oil filter adapter that the oil filter screws onto which is bolted into the block. Thats the bypass for when the filter gets dirty. The springs in the oil pump can be changed for more or less pressure.
 

wca_tim

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1,708
Re: Merc 5.7 normal oil pressure @ 3200 rpm's?

assuming you're running standard wt oil, etc... your pressures are just fine.
 

Polar_Bus

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Messages
131
Re: Merc 5.7 normal oil pressure @ 3200 rpm's?

HUH? The spring in the pump is just there to bleed off pressure when cold or high RPM's. Your thinking of the oil filter adapter that the oil filter screws onto which is bolted into the block. Thats the bypass for when the filter gets dirty. The springs in the oil pump can be changed for more or less pressure.

Correct, good catch, I was thinking one way, and typing another way. You know your "small blocks" :)

I edited my post with the correct info..
 
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