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  1. #1

    Default 1993 5.8l cobra can not throttle up

    Got my boat running the other day and took it out on the water it would only let me get about 1/3 throttle any more it would bog down and start backfiring. Ran around the lake a few times and then everything seemed to clear up still couldn't get full throttle but i was reaching speeds about 32 mph was getting ready to load the boat up and then it started acting up again. Couldn't hardly give it any throttle before it started backfiring. Things I have replaced recently are distributor, plugs wires, ignition switch, fuel filter and removed the anti siphon valve. I am starting to get very frustrated with this boat also put in new fuel with seafoam before last winter. I keep thinking it has to be something with the timing if anyone could help that would be great any ideas please.

  2. #2
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    5,144

    Default Re: 1993 5.8l cobra can not throttle up

    Ayuh,..... Probably runnin' lean from bad gas, or bad fuel flow,...
    Any Grease is Better,... Than No grease at All....

  3. #3

    Default Re: 1993 5.8l cobra can not throttle up

    gas is good but I think I might of figured out what is wrong. Checked the timing and it is set at about 7 degrees ATDC and when you give it throttle it goes even farther ATDC. Did a little research and the previous owner replaced distributor with one for a ford bronco. Could this be causing the timing advance to be backwards. if so I cant seem to find the original distributor available anywhere is there a replacement one that would work.

  4. #4
    Join Date
    Jan 2017
    Location
    Salem Oregon
    Posts
    54

    Default Re: 1993 5.8l cobra can not throttle up

    Quote Originally Posted by gpwannabe View Post
    gas is good but I think I might of figured out what is wrong. Checked the timing and it is set at about 7 degrees ATDC and when you give it throttle it goes even farther ATDC. Did a little research and the previous owner replaced distributor with one for a ford bronco. Could this be causing the timing advance to be backwards. if so I cant seem to find the original distributor available anywhere is there a replacement one that would work.
    im not sure this will help you, but I had the same issue once in a vehicle... it was found that the advance line was connected to the wrong vacuum port on the carb.... some carbs have different vacuum ports, one that pulls vacuum at an idle, and it drops away as the throttle plates open... and another that has no vacuum at an idle and creates vacuum as the plates open... look for a different port on the carb.

    also, 7 degrees ATDC?.... it should be closer to 10 BTDC... thats a big difference and would be creating some severe heat in the cylinders when pulling hard.

  5. #5

    Default Re: 1993 5.8l cobra can not throttle up

    got back to the boat today and adjusted the timing to 10BTDC but as i give it throttle and check the time it goes to about 14 ATDC can not get over 2500 rpm then it starts backfiring it is fuel injected so no carburetor. this distributor just has an electrical plug on it. anyone have any other ideas. I have about 32 psi of fuel under idle and under throttle not sure why it ran decent for that little bit on the water but now it is running terrible can't even get it to run good on muffs at the house

  6. #6

    Default Re: 1993 5.8l cobra can not throttle up

    also wondering if it could be an issue with the fuel regulator the rpm's move from 800 to about 1200 when at idle....should of said this earlier the boat sat for 3 years before I got it running I did change out the gas

  7. #7
    Join Date
    Jan 2017
    Location
    Salem Oregon
    Posts
    54

    Default Re: 1993 5.8l cobra can not throttle up

    have you tried unplugging the vacuum line and see what happens?.... it should run a LOT better than it does now, but still not a top performer.
    is the distributor original to the engine?

    try this and post your findings... remove the dist cap and see which way the shaft turns when you crank it (left or right).... then (with the engine stopped) unplug the vacuum line from the manifold and suck on the line.... which way does the advance mechanisim pull the distributor plate?.... if its set up right it should pull the plate in the opposite direction that the shaft turns.... if it doesnt it needs to be repaired or replaced, OR, as i said earlier, it needs to be plugged into the correct vacuum port if a reverse operating port is available...

  8. #8
    Join Date
    Jan 2017
    Location
    Salem Oregon
    Posts
    54

    Default Re: 1993 5.8l cobra can not throttle up

    I hit the send button and sent the last message before completing it... and maybe got the cart before the horse. distributors can be set up in many ways, but more commonly with modern distributors, as soon as the engine starts, the vacuum will pull the advance plate in the same direction as the shaft turns, and when the throttle plate is opened, the vacuum starts to fall off and the fly weights begin to take over and allows the plate to advance (to its at rest position)... you should check the fly weights below the plate and see if they are stuck.... ive seen them stick open and ive seen them stick closed, and either way, it will mess with the open throttle timing.

  9. #9
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    5,144

    Default Re: 1993 5.8l cobra can not throttle up

    more commonly with modern distributors, as soon as the engine starts, the vacuum will pull the advance plate in the same direction
    Ayuh,.... Marine distributors do NOT use vacuum,....
    Any Grease is Better,... Than No grease at All....

  10. #10

    Default Re: 1993 5.8l cobra can not throttle up

    was working on it last weekend and a buddy that knows more about boats than me stopped over and we found that the screen on the high pressure fuel pump was partially clogged and the bottom of that reservoir it sits on was very corroded on the bottom. cleaned the reservoir and screen and now it runs like a top. I was still getting normal pressure readings but obviously with more throttle need more fuel so the flow was restricted with higher rpms. Thanks for all the ideas.

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