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Thread: Oil pressure

  1. #1
    Join Date
    Mar 2009
    Location
    Dresden, Maine, United States
    Posts
    309

    Default Oil pressure

    Ok guys, I have an odd one for you. My boat has a chevy 270 (350 cu/in engine). I have a electric oil pressure gauge on it and when I start up cold it tells me I have 75 to 80 pounds of pressure. When I would get up to 2200 rpms it is around 75 pounds, get up to 3200 rpm and it starts to bounce all over the place. I then decided to put an mechanical gauge on as well. Start up and the electric gauge gave the same readings but the mechanical gauge would read 55 pounds. I would head out and run up to 2200 rpm and the mechanical gauge would read 25 lbs and the electric 75 lbs. increase the rpms to 3200 and the electric one stayed the same and the mechanical one would drop to around 10 lbs. There is no knocking or any noise when I get up in rpms.

    I am running 10/30 oil. The motor only has 58 hours on it. Any thoughts? One fellow suggested that the pressure relief valve where the oil filter screws on may be bad, The oil pan is a 5 qt model. I am at a loss and await every ones sage advice.

    Paul

  2. #2

    Default Re: Oil pressure

    That is a strange one. We tend to believe mechanical gauges but your electrical gauge has the more realistic numbers. Is the mechanical gauge plumbed next to the electrical sender ? Recommend trying another mechanical gauge. Needless to say, oil pressure is serious.

  3. #3
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,758

    Default Re: Oil pressure

    Quote Originally Posted by missnancy View Post
    ....The motor only has 58 hours on it.....
    Paul
    10/30 is a bit on on 'light side' regarding viscosity - what does the source of the engine have to say about viscosity?

    Pre-Y2K (old stuff), the rule of thumb was 10PSI of oil pressure for every 1000 rpm (@ operating temp)...having high pressure when cold is normal as is a drop as things warm up...

  4. #4
    Join Date
    Mar 2009
    Location
    Dresden, Maine, United States
    Posts
    309

    Default Re: Oil pressure

    The gauges are on a tee. What would be a better set up?

  5. #5
    Join Date
    Aug 2008
    Location
    Fairport, NY
    Posts
    1,624

    Default Re: Oil pressure

    "bouncing" oil pressure doesn't sound like a mechanical defect in the engine. Is it possible the oil level is very low or very high? At least one of your gauges appears defective.

  6. #6
    Join Date
    Mar 2009
    Location
    Dresden, Maine, United States
    Posts
    309

    Default Re: Oil pressure

    I just replaced the Mechanical gauge last week. The electrical gauge and sending unit last year

  7. #7

    Default Re: Oil pressure

    Try getting rid of the "T". Find 2 separate places to tap in, by distributor and one by oil filter. Put in fresh oil, straight 30 or 15w40. Is this a new issue? has anybody been inside the engine? Sounds like pan emptying out and not having good oil return from somewhere causing pump to run dry. Have seen oil pick up come loose from pump before causing weird oil psi problems. Also make sure you have the correct amount of oil in pan.

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