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2004 Yamaha 200 HPDI not getting higher RPMS

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  • 2004 Yamaha 200 HPDI not getting higher RPMS

    Hello, hoping someone has some suggestions before I just have to take it to be serviced. Motor won't run at any RPM's over 3700 - about 4000 or so. It seems to run fine at a cruising speed but go into the throttle more close to WOT and it bogs down and loses RPM until I pull the throttle back and RPM's will pick back up. Sporadically it would start losing a few RPM's after running awhile at cruising, sometimes it doesn't I've also sporadically been able to get it up to 4400 RPM or so and about 40mph and wouldn't bog down at WOT (although wouldn't get the max RPM's it should be either) I just bought the boat at the end of last season at which time it appeared to run fine and i was able to get about 45mph top end (boat is a Kencraft Challenger 206). Also interesting that when it starts to lose some RPM's, if I stop and pump the primer ball (which is flat after awhile, should this be staying hard?) it will run better for awhile.

    Ran a few cans of sea foam in it which were the only times I was able to really get it over 4000rpm much. I changed the fuel line from the fuel water separator and the ball and through the engine. Also pulled the VST tank apart and replaced that filter. Fuel water separator and canister filter were replaced when the service center winterized it at the end of the season last year. Hasn't been running well at all since I started using it for the season. Didn't know if it was just bad gas. Guy I bought the boat from had about 3/4 tank of non-ethanol gas in when i bought it last year. What else could this be? Injectors? one of the fuel pumps? Spark plugs? The "mystery filters" i hear about? Thanks.

    EDIT: Also, forgot to add I had some buy who works on motors briefly look at it becuase he happened to be at the place where I keep my boat and unfortunately he didn't have any of his equipment with him and we didn't get a chance to meet back up but in the few minutes he was looking over he immediately noted that it sounded 'obnoxiously loud" at idle and that the HPDI's are usually pretty quiet as far as 2 strokes go. Seems to make sort of a ticking or tapping kind of noise while its running. Also when it bogs down at WOT the motor kind of shakes.
    Last edited by jtav2002; 06-22-2015, 12:14 PM.

  • #2
    If the primer bulb goes flat there is a restriction between the motor and the tank and VST is running out of fuel

    Monitor fuel pressures to see, but sounds like it cannot keep up with fuel use

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    • #3
      Thanks. I'll try to investigate that further. If there is a blockage I guess it would have to be between the small clear canister filter housing and the VST since I replaced the line up to that canister.

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      • #4
        has to be on the south side of primer bulb if it is going flat
        maybe the pickup tube/anti siphon in tank valve

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