Oil pressure problems/ very strange!
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Oil pressure problems/ very strange!

  1. #1
    custom member raped southwind's Avatar
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    Default Oil pressure problems/ very strange!

    My 496 just got wet in the Daytona today but am having issues.
    Oil pressure hot idle 65-70 lbs. pressure is fine till 34-3500 rpms then it drops to 25-30 and I get out of it and oil pressure comes right back. Running a cast mercruiser pan with the pick up 3/8 off bottom. Wix racing filter.

    Orig I was told its a 7 qt pan but others have suggested it 8 qt?????
    I've tried running 7qts plus filter and tried adding another qt to make it 8 and problem now happens at 3000-3200 rpm.

    I'm thinking pressure bypass is failing , bypass in the filter is failing , or crank is drowning in the oil causing the the oil to foam?

    Any advise as I'd like to run the boat the rest of the weekend!

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    Some guy obnoxious001's Avatar
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    That's an open pan with no windage tray, correct? What oil do you have in it?

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    custom member raped southwind's Avatar
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    Quote Originally Posted by obnoxious001 View Post
    That's an open pan with no windage tray, correct? What oil do you have in it?
    Correct open pan, no windage tray but it does have a trap door in it. Running rosella 15-40 in it!

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    Senior Member SoldHondaBoughtHondo's Avatar
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    Quote Originally Posted by raped southwind View Post
    My 496 just got wet in the Daytona today but am having issues.
    Oil pressure hot idle 65-70 lbs. pressure is fine till 34-3500 rpms then it drops to 25-30 and I get out of it and oil pressure comes right back. Running a cast mercruiser pan with the pick up 3/8 off bottom. Wix racing filter.

    Orig I was told its a 7 qt pan but others have suggested it 8 qt?????
    I've tried running 7qts plus filter and tried adding another qt to make it 8 and problem now happens at 3000-3200 rpm.

    I'm thinking pressure bypass is failing , bypass in the filter is failing , or crank is drowning in the oil causing the the oil to foam?
    .


    Any advise as I'd like to run the boat the rest of the weekend!
    Fresh motor? Replace the filter....7qt pan looks like a car pan with a sump..not familiar with an 8qt....increase in rpm and oil pressure increases to a point and then takes a dive is usually a restriction in flow
    It the crank is swinging in the oil it will take it a while to start and it needs more that 3500 rpm unless it's major overfill...When it does it shut it right down, wait 30 seconds and restart..if pressure is still crap let it sit for 15 min and restart..better pressure usually means air in the oil...

    Knowing exactly how much oil is in the pan is a good thing...8 qts in a 7 qt pan is asking for problems.....

    And if ya want real odd oil pressure issues try running a 455 olds in a v-drive with a jet pan and pickup and the trap doors removed. It needs 7 1/2 qts..in a 10 qt...+- 1/2...less and it tends to suck the pan dry and more had the crank swinging in the oil.....motor has run 5k for almost 2 min....twice...and hasn't broke yet
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    gn7
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    Quote Originally Posted by raped southwind View Post
    Correct open pan, no windage tray but it does have a trap door in it. Running rosella 15-40 in it!
    get rid of the oil. The stuff can't tell if its suppose to be oil, or whipping cream. Tons of detergents=foam. Plus it loaded with calcium to up the TBN number(long life and drain intervals) and that adds to the foaming as well. You have an oil that was designed for a low RPM diesel truck, not a performance engine.
    Does it have an oil cooler?
    Is this a 8.1 Merc 496, or a home built 4.25 stroke 496? MK IV block, or a Gen 5-6



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    Last edited by gn7; 09-08-2012 at 12:18 AM.

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    Quote Originally Posted by gn7 View Post
    get rid of the oil. The stuff can't tell if its suppose to be oil, or whipping cream. Tons of detergents=foam. Plus it loaded with calcium to up the TBN number(long life and drain intervals) and that adds to the foaming as well. You have an oil that was designed for a low RPM diesel truck, not a performance engine.
    Does it have an oil cooler?
    Is this a 8.1 Merc 496, or a home built 4.25 stroke 496? MK IV block, or a Gen 5-6
    Much as i hate to admit it, you right again
    Don't notice the rottilla comment until just now. Tried it one time...nothing but flaky oil presure
    "A liberal paradise would be a place where everybody has
    guaranteed employment, free comprehensive healthcare, free
    education, free food, free housing, free clothing, free
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    not, such a place does, indeed, exist: It's called prison."

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    Senior Member hellnback's Avatar
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    It may be OLD ,it may be Slow ... but at least it's MOBILE !!!

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    custom member raped southwind's Avatar
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    Will dump the oil today and swap the filter. Not a merk 8.1 it's a stroked crank. Pan looks like a car pan with an extra 3-4 in added to the front of the sump.
    Last edited by raped southwind; 09-08-2012 at 08:10 AM.

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    Quote Originally Posted by SoldHondaBoughtHondo View Post
    Much as i hate to admit it, you right again
    Don't notice the rottilla comment until just now. Tried it one time...nothing but flaky oil presure
    It's amazing how many people use diesel oil in boats. It seems like I read alot these things oil pressure is acting weird threads and they don't know why but they are using diesel oils. Rarely hear it with people using Valvoline VR1 20-50. Not saying it doesn't happen just seems like a lot with diesel oil. Hi quality conventional oils designed for gasoline is all the protection you need.


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    I had the same issue with the oild pressure dropping and then coming back up. My system one filter was full of terry cloth.
    Your filter could be full of matter that got into the motor while buildiing it, and for sure get some good oil it her.

  13. #11
    gn7
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    I have serious doubts the filter is a problem. Even if it was clogged, which I doubt, it does have a bypass, and I don't think it bad.
    But as long as I am bringing in the filter, you could not possibly have chosen a worse break in filter. It has by far the highest flow, but it also allows by far, the largest particles to pass thru. It has a micron rating of 60 plus compared to a regular Wix of around 12 micron. Great filter....if you're actually racing, and you really need to flow 20 galllons per minute.

    Get a regulare Wix, NAPA, K&N, Mobil 1, or Baldwin. If the block mounted bypass has been removed, put it back.

    If you still have problems, you can address them after you do the above.



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    Thanks for everyone's help..... Dropped the oil and filter and put vr 20-50 and only put 6 qts in. Problem solved. We are all good!

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    Also this is not a fresh motor. Short block had 10 hrs

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    Super Moderator HammerDown's Avatar
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    Quote Originally Posted by raped southwind View Post
    Thanks for everyone's help..... Dropped the oil and filter and put vr 20-50 and only put 6 qts in. Problem solved. We are all good!
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