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Low oil pressure in mercruiser

  • Thread starter interprosystems
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interprosystems

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"i have a 1981 cobalt w/ a 260

"i have a 1981 cobalt w/ a 260 mercuiser v8 engine. i recently had the heads replaced & she runs like a top. one problem though: oil pressure is low, like at 25 psi regardless of rpm. owners manual says it should be 30-55 psi. @ 2k rpm. oil pressure gauge & sender were recently replaced so i dont think they are mis- reading. engine runs strong & cool - approx. 130 degrees.

could the oil pump be failing?? if so, what is required to replace it?? pull motor?? yikes.
any other options ideas?? any way to check to see if oil gauge is reading properly? or if oil pressure is actually ok??

thanks."
 
"personally, i would either le

"personally, i would either leave it as is and not worry about it or do the above."
 
"DON'T keep running it or

"DON'T keep running it or it WILL have to come out. Do as Bt recommended and see if you really have a problem. Sender units--new and old--can lie to you, as can gage heads.

JEff"
 
"If the pressure is found to b

"If the pressure is found to be low with the test gauge,you may have worn cam bearings. Was the pressure ok before the head work was done? Why did you have the head work done? Does this engine have a lot of hours on it? You may want to listen close while changing the rpm from idle to about 2200. Just up and down in rpm and see if you hear any knocking in the lower part of the engine.(bearings going south) I've found the oil pump doesn't fail very often. You could get lucky and have a bad bypass in the oil filter mount. In any event,sounds like you better start saving your dimes and quarters. Looks like a new engine is ahead."
 
"Just to pile on...

Get a m


"Just to pile on...

Get a mechanical gage on it. Isn’t that 260 a Chev derivative? I've seen idle oil pressure at 5 - 10 lbs and not be a problem (cars). If you indeed have 25lbs, you might be fine.

My experience tells me that oil pressure problems show up at idle first. Worn out main bearings would be the first thing i would suspect."
 
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