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94 Prostar 205 350 Indmar tbi - Bogs on hard acceleration

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  • 94 Prostar 205 350 Indmar tbi - Bogs on hard acceleration

    I have had 2 marine mechanics look at this and replace most parts related to the fuel supply (one of them substituting parts from his own inventory to see if a specific part was a problem and to save me needlessly buying a new part that didn't solve the problem.) I asked each of them if it might be something as simple as an anti-siphon valve coming from the gas tank, but both have said this boat doesn't have an anti-siphon valve. Boat is 5 hours away so I can't go look at it until my next trip out there. I'd appreciate advice on whether this boat woud have an anti-siphon valve, and if so, a $10 part might fix what has cost me a lot of money in mis-diagnoses.

  • #2
    Originally posted by Alberta View Post
    I have had 2 marine mechanics look at this and replace most parts related to the fuel supply (one of them substituting parts from his own inventory to see if a specific part was a problem and to save me needlessly buying a new part that didn't solve the problem.) I asked each of them if it might be something as simple as an anti-siphon valve coming from the gas tank, but both have said this boat doesn't have an anti-siphon valve. Boat is 5 hours away so I can't go look at it until my next trip out there. I'd appreciate advice on whether this boat woud have an anti-siphon valve, and if so, a $10 part might fix what has cost me a lot of money in mis-diagnoses.
    I have a 93 (same generation era as your 94). Mine has (or did until I replaced it otherwise). I suspect yours does but I could be wrong. However that is one of several possibilities of the top end stumble.

    You can easily get to that fuel assembly by rotating the fuel cell about the axis of the fuel filler hose, out onto the floor, leaving the fuel cell and filler hose attached to the boat. Your 205 and back seat / transom area may be different than the 93 190. Photo of my 93 for example.

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    Click image for larger version  Name:	Anti Siphon Check Valve fuel cell.jpg Views:	0 Size:	42.8 KB ID:	2707687

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    Click image for larger version  Name:	fuel cell05a text.jpg Views:	0 Size:	85.0 KB ID:	2707688
    Last edited by waterlogged882; 06-21-2022, 11:30 PM.
    93 190
    (safe click)

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    • #3
      Post script: after thinking a little more, I want to change my mind. Your 94 has an electric fuel pump where the 93 was the last year of mechanical fuel pumps. I say yours does not have the valve. No need with the different design of fuel pump. That is my final answer.

      You have a nice setup in the 205 and the 94 year make. Hang on to it. The next generation hull changed in 95.

      Best on the solution.
      93 190
      (safe click)

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      • #4
        I recommend following sound troubleshooting, and I am not sure you have a fuel issue. Sometimes it could be timing related. To me that motor is particularly sensitive to old gasoline. Make sure you have fresh fuel, clean fuel filter and a sound fuel pump. Injector spray should be checked to make sure fuel is sprayed and not dumped into throttle body,

        rotor, cap, plugs all good?

        if you are feeling brave, loosen the lock bolt on the distributor and test rotation or mechanical advance in each direction at idle and see if the situation changes, sometimes a little movement in either direction may give you a better advance adjustment for acceleration.

        someone shared the MEFI troubleshooting manual on TeamTalk, let me see if I can find it.
        Ski in snow, ski in water, and always have fun!

        2008 Prostar 214 MCX
        1995 Prostar 190 "Evil Minion"
        Previous 93 Prostar 190 1.5:1 GT40

        "Left Foot Forward and preferring girls."
        "Do you have Flake on that boat?"

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        • #5
          Your 94 should have a valve at the fuel line - make sure it's open all the way.
          1. Are you getting black smoke when it stumbles, example of being way to rich.
          2. Did anyone look at the ICM, located under the distributor cap? Easy to change if anyone has a spare.
          3. Will the boat accelerate but not reach full rpm, under smooth throttle, not hard full throttle?

          For some reason, my 94 had this problem twice and each time it turned out to be a wadding of paper like substance(sort of Q-tip like) on the FINE MESH screen at the bottom of the fuel pump. You have to take the bottom fitting off and then you'll see the screen.
          My LT1 had a subtle stumble every now and then and I found this when I put in new fuel lines in the bottom of the fuel pump. No more
          1993 25th Anniversary Limited ProStar 190, #17

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          • #6
            1993 25th Anniversary Limited ProStar 190, #17

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            • #7
              Bret, thanks for the feedback and photo. I learn something everyday.

              What I learned today is to stay out of Chevrolet engine threads.

              .
              Last edited by waterlogged882; 06-22-2022, 01:22 PM.
              93 190
              (safe click)

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