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Thread: 500efi

  1. #1
    My Boats:
    28 Pantera
    Join Date
    May 2007
    Toronto Ontario


    I was wondering if some of you could give me some insight regarding these engines.
    Common problems
    Recommended Service Intervals
    #hours before parts failure/ rebuild

    I am looking at 2 boats and they both have 500EFI power.

    Thanks in Advance

  2. #2
    My Boats:
    '06 35 Lightning Merc HP 525's aka The Black Biotch
    Join Date
    Jan 2004
    Northern NY
    HP 500 EFI or carb are same basic animal, you can dig out a lot of info on here about them.

    Basics, 200 hrs change the valve springs, spend some bucks and get quality springs, shims and retainers. Check the chit every season for signs of problems. Check the Crane roller rockers seasonaly and plan to replace around 200-250 hrs, or just change to the Crowers and forget them. Plan on changing the roller lifters around 250-300 hrs. Other than the valve train they are good motors, most all failures have been valve train related. When I had to rebuild mine it was a broken valve spring that caused it, dropped a valve, was very lucky did not do much damage other than mark the top of the piston, the internals were all fine, that was at 176 hrs. I would own them again, but would just use beter quality parts than Merc did in the valve train. A few xtra bucks will save you in the long run. Have someone do a leak down test on any you are looking at and you should be fine.
    Last edited by RaggedEdge; 02-22-2008 at 01:10 PM.

  3. #3
    Join Date
    Jan 2005

    500 efi's

    I have had several of them and had no problems.
    They are very reliable.
    I have a friend that has 500 hours on his and he runs them pretty much WOT all the time.
    O problems for him.
    Depending on the boat they are pretty good on economy and you can run 87 octane in them which is nice.
    I have been very pleased with mine.

  4. #4
    Charter Member #34 Charter Member Dock Holiday's Avatar
    Join Date
    Oct 2000
    Beautiful North Carolina
    The best most reliable most race proven power plant in the marine industry.

  5. #5
    Join Date
    Jan 2004
    Jacksonville FL
    what about borring them over 30 over? do you start to see unreliabilty with small engine working

  6. #6
    Platinum Member Platinum Member
    My Boats:
    fuel injection, superchargers
    Join Date
    Jan 2001
    PA and MD
    What do you do to the 500EFI to get to 620HP? Heads, cam? Cost?
    Cobra Terminator 3000, single engine 30' true tunnel cat
    Home of the "ON-BOARD-DYNO"
    Stellings Bravo Extension Box with a built-in DYNO!
    Reads 0-1000HP and 0-1000TQ in the water, on the fly, while you drive!
    Search OSO 'on-board-dyno pictures" for details.

  7. #7
    Platinum Member Platinum Member Top Ven's Avatar
    My Boats:
    Nor-Tech 390 Sport CC
    Join Date
    Jul 2007
    New Jersey
    i have 280 hrs on my 500 efi in my Top Gun, i would like to get them to 620 hp, Who does that work ?

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