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Thread: BBC Oil Pressure Issue

  1. #1
    cyclone
    My BBC shows 70psi of oil pressure when cruising at 4,000rpm. If I floor it, the pressure will drop all the way down to 20psi by the time the motor spins 5,000rpm. According to the gps, the boat is still building speed, but i have to let off the gas because of the drop in oil pressure. If i ease into it, the pressure will hold at 60spi. Its almost like the oil pump is cavatiting. i have a 10-quart pan on the motor, but i dont know if its got a trap door or windage tray. Any suggestions? I was considering going to a thinner oil.

  2. #2
    Clown
    Cyclone!
    I've had that same problem when I used Royal purple Oil Racing#9 weight. It did make 10 more HP on the dyno but I would not recomend it to be used in a pleasure boat!!!The 6th pass I had that problem with it not wanting to build oil pressure When it was up to temp.So I would not recomend a thinner oil!
    My problem was that I started to wipe out a couple of main bearings.
    Now I'm just an a$$hole !!!!!!!????
    So dont listen to me I'm just saying that I had almost that same problem.
    ???Maybe your pump pick up is cavatiting when you excelerate hard,It might just be in the wrong location and not the pick up or the pump at all! eek! I'll start smokin my crack pipe now eek!
    And see if any of my buds have run into that same Problem!!

  3. #3
    cyclone
    ok so dont go thinner with the oil then? i'm all out of crack.

  4. #4
    Clown
    Right
    If anything go with the mercury racing oil I think its 15w40 but not exactly sure on that number its been awhile since I've run that stuff.
    It is good stuff dont get me wrong!

  5. #5
    cyclone
    i wonder if this is just an oil weight problem or if there is something else going on?

  6. #6
    comin' unscrewed
    Is this a new motor, or did the problem just develop?
    If it's new - did you check the clearence between the oil pickup and the bottom of the pan?
    New or not - I've had the plunger in the pressure relief get sticky on a couple of motors. They did EXACTLY what you descibe. I had to pull the pump and then I applied a little valve lapping compound to the plunger and spun it with a hand drill. Solved the problem both times.
    By the way, one of these was brand new pump.

  7. #7
    cyclone
    I just bought the boat and the owner says that the motor had only and hour on it.

  8. #8
    Clown
    Also their is a bypass built into most oil filters!

  9. #9
    Senior Member
    Join Date
    Jun 2009
    Posts
    10,871
    If it's new - did you check the clearence between the oil pickup and the bottom of the pan?
    New or not - I've had the plunger in the pressure relief get sticky on a couple of motors. They did EXACTLY what you descibe. I had to pull the pump and then I applied a little valve lapping compound to the plunger and spun it with a hand drill. Solved the problem both times.
    By the way, one of these was brand new pump.
    I agree, we've seen both these problems and they can cause what you are describing

  10. #10
    Clown
    Rex one I'm in the process of building a 496BBC with twin turbo's . Please E:Mail me If I can twist your Brain a little

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