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Old 07-07-2010, 12:48 AM   #1
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Default oil pressure normal?

2005 1900 sr3 mercruiser 4.3 190 h.p. Idle pressure is approx.60 psi
under load boat on plane running 30 mph pressure is approx. 75 psi
does this seem high or is this normal?
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Old 07-07-2010, 04:29 AM   #2
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sounds like your gauge might not be set right.....but if you got 75psi...dang that's good!!...what you really need to worry about is low pressure...all the way down to 15psi...I think the specs say it can run all the way down to 5psi before damage is done..

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Old 07-07-2010, 02:12 PM   #3
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I think your gauge is a little optimistic but yeah, these engines run high volumn, high pressure oil pumps.

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Old 07-07-2010, 07:17 PM   #4
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Thanks for the response,
I had an auto mechanic tell me he thought the high pressure might be caused by a sticking check valve,and I might damage the bearings or blow an oil seal if I continued running with this much pressure.Sounds like you guys aren't at all excited about the high side,makes me feel a lot better!
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Old 07-07-2010, 07:47 PM   #5
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There could be two check valves, definately one on the oil pump (actually a high pressure relief valve) and possibly one on the oil filter assembly. The latter will not/cannot cause high oil pressure.

The OP relief valve could possibly stick closed but I think it is unlikely. While high oil pressure might possibly cause a oil seal issue (he's likely referring to the rear main seal) you'd have already seen that if it went. As to bearing damage frm high oil pressure, I'd be interested to understand his rational. If he had said damage to the distributor gear, or the oil pump drive pin, I could understand his concern.

Settle the matter by temporarily installing a mechanical oil pressure gauge.

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Old 07-08-2010, 04:27 PM   #6
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Since the oil pump is only pushing oil up through the filter ,crank bearings through the galleries up into the push rod to your rocker gear and then gravity flow back to your sump lubricating everything else on the way down to be picked up again the pressure cant effect the sump seals. What dose effect the sump seals is exes sump pressure usually crated by blow by from bad compression rings
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Old 07-08-2010, 05:09 PM   #7
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one of the bearings that can be damaged are the cam bearings..they get oil directly from the pump and can cause a bearing blow out...or journal damage....

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Old 07-08-2010, 06:30 PM   #8
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Struggling to understand that Steve......
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Old 07-08-2010, 07:25 PM   #9
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well...the journal bearings that hold and lube the cam as it spins gets it's oil supply directly from the pump...there is a hole in the journel that allows oil to flow around the cam...when you get too much pressure from the pump...the oil will actually wear a path to the side of the bearing depriving the cam of it's lubing capability as it spins....thus wearing the bearing out (oil starvation) and the part of the cam that rides on that bearing....when you build an engine up....you will have a set of cam bearings that need to be popped in and the old ones popped out...it's simple but it's a pita when you have to do it....

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Old 07-09-2010, 01:21 PM   #10
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I suppose that's possible but I gotta say that I have neither seen nor heard of bearings damaged by too much OP, ever, and would think it would require some very serious pressure. Additionally, as the cam spins, it actually pulls the oil around the circumference of the journal. Nevertheless, I've seen some weird stuff happen in these engines and I hope none of them happen to the roller cam 489 I have on the engine stand right now. LOL

Without getting into how oil is routed through these engines, or how all the bearing clearances add up to one very large controlled leak, I don't believe SRVFAN has a serious problem. Besides, I think the oil filter would rupture way before any other hard parts could be hurt.

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Old 07-09-2010, 02:11 PM   #11
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I had that done to my corvette engine way back when I rebuilt it...had to tear it down and replace the bearings in the cam...so..it happens...and if it's something weird..it will happen to me...

as for the filter blowing out...no..the bypass valve will lift before the can ruptures....but if the can on the oil filter ruptured...that would be in the weird range again....it would happen to me...

with that said..if he's got that much oil pressure..then indeed he does have a problem with either the gauge or the sensor since I doubt his oil pump could put out that much pressure...it's just not designed to pump that much oil pressure..

imho..
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