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Results 1 to 12 of 12
  1. #1

    Default 502 EFI Falls on its face

    I have a 502 EFI that once on plane it falls on its face. I can pull back to half throttle and it will pick up again. Also when I hit some rough water and the boat starts rocking it will also cut out. Bypassed fuel tank switch and still same issue. Runs at idle with no prob. Thanks!!

  2. #2
    Join Date
    Jul 2011
    Location
    Naknek, AK
    Posts
    3

    Default Re: 502 EFI Falls on its face

    Brett, I am interested to hear more about your engine problem. It sounds like it is doing the same thing as my 502 PFI. Mine seems to be fine for the first 1/2 hour or so of operation, then all of a sudden it will miss, backfire, drop off plane, etc. If I pull back on the throttle it will catch itself and I can add power again. It is totally random when it happens. On the last trip out it did it and it finally quit and now I have no spark. So that makes me think it is an electrical problem in my case. What year is your engine?

  3. #3

    Default Re: 502 EFI Falls on its face

    Its a 1996. My boat does it all the time. Once on plane and at full throttle it will just drop out kind of like you shut the key off then back on again. Then it gets worse as I keep going. Just stalls out and sputters. But the weird part is once on plane and the boat starts rocking from hitting waves its drops out also..I have no idea so far...I will keep you updated

  4. #4
    Join Date
    Jul 2011
    Location
    Naknek, AK
    Posts
    3

    Default Re: 502 EFI Falls on its face

    That sounds just like mine, except that mine seems to do it after about a half hour of running. Then it does it all the time. Just like you said... like you turn off the key? If I figure it out I will let you know.

  5. #5

    Default Re: 502 EFI Falls on its face

    Ok, I have mine in the shop right now AGAIN...HA....I will keep you updated also. Thanks!

  6. #6
    Join Date
    Jul 2010
    Location
    Canada
    Posts
    630

    Default Re: 502 EFI Falls on its face

    Have you checked your battery cable connections? Check both pos and neg cables at batteries and engine. Make sure clean and tight. Other possibilities are failing coil; starts acting up once hot, ignition switch; start the engine then jump the run circuit on the switch and go for a ride, and the kill switch if you have one; again, jump it with a jumper wire and go for a ride. As always with multiple possibilities, try only one at a time so you can actually determine which fix worked and hense find out what was causing the issue. Keep us posted.

  7. #7
    Join Date
    Jul 2011
    Location
    east tennessee
    Posts
    9

    Default Re: 502 EFI Falls on its face

    Maybe the fuel pickup is getting clogged . The crud falls away into suspension for a while then after some runtime it plugs up . After sitting for a spell the crud falls back into suspension again . Using gasohol (10%) on a regular basis will loosten up any kind of buildup that has been present in the tank . It will pass enough gas to run low RPMs with no miss but it takes volume to run the big RPMs . That tank screen is your fuel systems first line of defense . Just a thought .

  8. #8

    Default Re: 502 EFI Falls on its face

    Thanks guys.....Still waiting to get it back from the shop...I have passed on your info to them....We shall see.

  9. #9
    Join Date
    Jul 2010
    Location
    Canada
    Posts
    630

    Default Re: 502 EFI Falls on its face

    Ditto mountainman. You can eliminate the vessel's fuel supply system by hooking up a portable fuel tank to the engine and going for a ride. If the problem persists, it's at the engine end.

  10. #10

    Default Re: 502 EFI Falls on its face

    Looks like they are starting with the fuel regulator pump under the manifold.....We shall see....

  11. #11
    Join Date
    Jul 2011
    Location
    Naknek, AK
    Posts
    3

    Default Re: 502 EFI Falls on its face

    Brett, Wanted to give you an update on my 502 w/ issues. Mine turned out to be the ignition control module in the distributor. It would have been fixed a week or so ago, but had to wait for the part to come. While doing research online, I found my 502 symptoms were to a tee for the ignition control module going bad. (Only failing when it gets hot, after it cools off it works again, then total failure / no spark) May not be your problem, but keep it in mind for the future. I got out of it for less than $100. Hope you have the same luck and they fix your problem.....Happy Boating!

  12. #12

    Default Re: 502 EFI Falls on its face

    OK, Long story short...We had to remove the VST tank and mecanical fuel pump. We ran return lines with bigger fuel lines back to both tanks and put in an inline fuel pump. Prob solved. The VST tank is the root of all evil. Thanks for all your posts and ideas!! If your in Phoenix, take your **** to Mark at Speed Sports in Mesa!!

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