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  • top speed

    Want to start off on saying im a newbie her. Spoke with a guy online today and told me to check this site so here I am. He we go guys. I bought a 1980 marlin open bow jet boat with a 460 I was told it has some engine work done to it. It has a mild cam electronic ignition. So before i bought the boat it had been sitting for a couple years. The first time I took I out it gps at 52 mph that was last summer. So the time I took it out this year I replaced the 600 cfm holly to a 670 cfm street avenger. So im at the lake now its in the water and runin im at the wheel my buddy is at the carb adjusting while im driving and then he goes to the timing plays with that. As all this is being done I got my gps going and TOP SPEED is 43 mph. I havent done this yet but im thinking of changing the fuel filter im wondering if that would have an impact on the performance. Also my boat has a cover over the engine so the engine compartment is completely closed I opened a section at the front to get some fresh air. Any help would be greatly appreciated.

  • #2
    Re: top speed

    Welcome to the site.!!

    You will probably get some better advice from someone else later, but for now id say you cant go wrong with a new filter EVER.
    A new filter can't hurt anything so if you got one go for it. If you got one you can see inside it, see what it looks like if it was sitting for a while it could need a few changes. Always start with the easy, & cheaper stuff.

    The boat should be getting enough air, since that was how it was built, but again it can't hurt to try giving it more.

    What RPM we're you getting before when it ran 52mph.? (and what are spinning now?)


    Probably wont fix it overnight.. boats are projects, & there is always something that can be improved.
    Let us know how its coming.. Good Luck

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    • #3
      Re: top speed

      What did your buddy set the timing at? Did he use a timing light? Check the jetting and air bleeds in the new vs old carburetor. Curious as to why you changed it to begin with? Try putting the old one back on see if that makes a difference.
      Good luck!
      BW1
      Ever wonder why boogers only smell after you pick em?

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      • #4
        Re: top speed

        Originally posted by bwurst1 View Post
        What did your buddy set the timing at? Did he use a timing light? Check the jetting and air bleeds in the new vs old carburetor. Curious as to why you changed it to begin with? Try putting the old one back on see if that makes a difference.
        Good luck!
        BW1
        Thanks for the info guys. I did change the fuel filter and also my buddy change the timing just by listening to the engine he did not use a timing lightthe reason I change the old carburetor was due to the popping and was told that my boat would probably run better with a little bit bigger carburetorthe guy that I got the carburetor from told me that he had put bigger jet in the carburetor which I do not know what jets are in now. I don't know what else to look for or what else to do I have change the fuel filter I have looked in the impeller nothing if stuck inside everything looks good. could my fuel pump be going bad I don't know if that would cause that but my boat runs good sounds good its not starving for fuelnot sure what else to look for thanks guys for all the info once again I could use all the help I can get

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        • #5
          Re: top speed

          You can not set the timing by ear and know its right. You can loose a lot of power by having the timing off and if hes doing it by ear I'm betting its way off. Is it running rich? Bigger jets mean more fuel too much fuel can cause a loss of power. Lean=fast, too lean=boom.
          Ever wonder why boogers only smell after you pick em?

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          • #6
            Re: top speed

            Originally posted by haypuppy View Post
            Thanks for the info guys. I did change the fuel filter and also my buddy change the timing just by listening to the engine he did not use a timing lightthe reason I change the old carburetor was due to the popping and was told that my boat would probably run better with a little bit bigger carburetorthe guy that I got the carburetor from told me that he had put bigger jet in the carburetor which I do not know what jets are in now. I don't know what else to look for or what else to do I have change the fuel filter I have looked in the impeller nothing if stuck inside everything looks good. could my fuel pump be going bad I don't know if that would cause that but my boat runs good sounds good its not starving for fuelnot sure what else to look for thanks guys for all the info once again I could use all the help I can get
            If its poping out the carb.to retarded..popping out the exhaust..to rich or to much advace...check your float level..and look for vacum leaks

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            • #7
              Re: top speed

              Originally posted by Gone Green View Post
              If its poping out the carb.to retarded..popping out the exhaust..to rich or to much advace...check your float level..and look for vacum leaks
              Wrong spring in the Vac secondary? Sounds like they aren't opening. It should run better with that carb.

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