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Thread: Oil Pressure/Temp

  1. #1
    Hey guys. Now that my boat is on the water I have a question regarding oil pressure/temp.
    I don't have an oil temp gauge.
    I'm running a 454 .030" over 9-9.5:1 500hp/500ft lbs motor in a jet boat spinning a Legend A impeller. I mostly run up around 3500-4000 RPM with the occasional 5,000RPM bursts here and there. The oil pump is a Melling M77G pump. I cannot remember for the life of me what weight oil I put in this motor when I changed it after the break in, but my question is...
    When the engine is cold (first startup of the day) it idles around 50psi. However, after I've been running around the lake and the engine and oil are good and warm my idle pressure drops to about 25psi. When cruising it's right back up at 50...but at idle it's at about 25. Should I be running an oil cooler? Or will running a heavier weight oil help the situation?

  2. #2
    Havasu Carrera
    I ran without a cooler for a while in my jet boat and always had the same problem. Sometimes it eaven lost pressure at high rpm so I would slow way down or just stop and let it cool. When I put it in the stern drive and added the cooler ( I know different situations) the motor NEVER looses pressure and the temp on the oil and water is always real cold. On the jet the water temp was 0 all the time but not at idle.Hope that helps a bit. OH and I will NEVER run without the oil cooler again.

  3. #3
    I fail to see where your "situation" constiutes a "problem".
    I am running a STOCK GM oil pump, cold idle oil preessure is 53PSI, cruising or wound out hot oil pressure is 58PSI, hot idle pressure is 23PSI.
    Oil is Castrol Syntech 20w-50.
    You know our motors are ALMOST identical.
    3rd year right now, and no problems, at all.

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