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  1. #1
    Join Date
    Jun 2014
    Location
    Lexington, KY
    Posts
    185

    Default PCM 454 Oil Pressure?

    What is "normal" oil pressure on a PCM 454? My boat has 1250 hours, and my gauge reads just about 20psi when at normal operating temp at idle, and 45-50 at WOT. The oil pressure dummy light and alarm will chirp at me coming back to idle. Sometimes on solid at idle, if it's warmer and pressure settles barely under 20 at 500rpm. Oil is already a little heavier Rotella 15w40.

    This all seem a little low to me, and I had a buddy onboard that has a Mercruiser 454 based engine that run nearly double those numbers all the time. But his engine is a WAY different beast - the Mercury "Blue" 500 Bulldog in a Fountain...

    I guess first step is to verify these numbers with a mechanical gauge, but what should i really be expecting?
    Korey Morris -
    Sold to Arkansas: 1986 Supra Saltare
    Current: 2018 Moomba Craz

  2. #2
    Join Date
    May 2013
    Location
    Burden Lake NY
    Posts
    272

    Default

    My 454 with about 800hrs holds 40psi at idle, and 60psi+ at any engine speed above idle. Your numbers do seem a little low, but not horrible. You have already verified your oil pressure since you have a gauge, but swapping it out with a known good gauge won't hurt to double check pressure readings. There is a very old automotive rule of thumb, that dates back to when these engines were manufactured. 10psi of oil pressure for every 1000rpms being acceptable. So at 5k rpms you should have 50psi, 3k rpms 30psi and so on. If you choose to use this age old rule of thumb, then you are still with in acceptable limits, albeit on the lower end of the spectrum.

    In all reality, with the thicker oil, and still showing lowish oil pressure, your engine is probably getting worn out and will be in need of a rebuild sometime in the distant future. It's quite possible that it will run just the way it is for a very long time, a lot of it depends on how you use your boat. If it were me, i wouldn't lose much sleep over it because there isn't much you can do to fix oil pressure with the engine in the boat. Keep an eye on it and enjoy it as you would normally. Rebuild or replace when the time comes.
    1988 Supra Sun Sport 454 PCM
    1972 Olds Cutlass 455
    1998 BMW 750il
    1996 BMW M3 coupe
    1995 Toyota Tacoma 4x4

  3. #3
    Join Date
    Jun 2014
    Location
    Sydney Australia
    Posts
    80

    Default

    Just to throw it out there but you have checked your oil level

  4. #4
    Join Date
    Dec 2013
    Posts
    645

    Default

    As a guide, you should have at least 10psi per 1,000rpm. So, the numbers you gave are fine, so long as the gage is correct. If you have 20 at idle but are still getting the chirp, the low pressure switch may be going bad.

  5. #5
    Join Date
    Jul 2011
    Location
    fort worth , tx
    Posts
    1,171

    Default

    Just don't be like my Windsor and have 20 psi at 6000 rpm . Lol buy a manual gauge and verify . Real easy to blow a bottom end without correct oil press


    Sent from my iPhone using Tapatalk
    LIFE IS TOO SHORT NOT TO BE LIVELY

  6. #6
    Join Date
    Jun 2014
    Location
    Lexington, KY
    Posts
    185

    Default

    LOL, yes it has oil, but thanks for thinking simple for me! I've put almost 200 hours on the boat in 2.5 seasons now, change the oil twice a season, and it has been like this since I bought it. I wasn't concerned with it until my buddy raised the red flag. I'll take my mechanical gauge this weekend to verify, and stop worrying about it. Maybe I'll unhook the buzzer... I can also bump my idle up a touch now that I'm running a 13x11 prop - 500rpm was coming out to be 3.5 MPH int he idle zones last weekend. I could stand to move jsut a little quicker at idle anyway.
    Korey Morris -
    Sold to Arkansas: 1986 Supra Saltare
    Current: 2018 Moomba Craz

  7. #7
    Join Date
    Oct 2012
    Location
    Guelph Ontario
    Posts
    528

    Default

    I went down the rabbit hole a couple of years back and read a bunch of stuff on bobstheoilguy.com. One mistake a lot of people make is putting thicker oil in to get the oil pressure up. Flow is more important than pressure, so thicker oil may bump your pressure up a bit, but it can lower your flow. Oil is not only for lubrication but also for cooling. Just my .02

  8. #8
    Join Date
    Apr 2012
    Posts
    223

    Default

    Isnt the oil rating higher? Mine is 20w50 iirc for my 350

    Sent from my SM-G920V using Tapatalk

  9. #9
    Join Date
    Sep 2010
    Location
    Collegedale, TN
    Posts
    1,905

    Default

    My 454 is freshly rebuilt and I'm at 30 at idle and about 65 at speed. Your numbers certainly don't sound too low for a "mature" engine. You're running the right oil and those numbers are fine until they start dropping more.

    1986 Saltare
    Restoration link: http://supraboats.com/bbs/showthread.php?t=7839

  10. #10
    Join Date
    Apr 2012
    Location
    Tacoma, Wa
    Posts
    861

    Default

    Verify the ground to the gauge is good. Take note if the pressure drops or rises when you turn on electric loads. This is a sign of a poor ground.
    2003 Supra Launch 22SSV
    1986 Ski Natique 2001

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