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Thread: 300 HPDI Mods

  1. #1
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    300 HPDI Mods

    Just purchased a 22 Activator with a 300 HPDI Yam on it from the Doc. Some of you may have put more power & or reliability into keeping these engines alive and healthy. I'm all ears for your suggestions and experience with these engines. TIA for your replies.


    Forgot to add that I know about Hydro-Tech and did do a search on here about the HPDI.
    Last edited by FrankU; 07-12-2017 at 07:40 AM. Reason: Additional statement

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    I have a pair of 300 vmax hpdi's on a 23' eliminator. Both have hydrotec stage 2 kits, which includes the high compression heads, solid motor mounts, and shortened tuner. The heads raise compression from the stock 87 octane friendly 115 psi up to a more 300xs-ish 135 psi. You have to run 91 or better octane.

    I found that modifying the stock airbox can net a 2 mph gain. I did back to back testing and repeated this. Maybe we can work out a trade because one of my motors has a modified airbox and hydrotec reeds/cut reed cages. I'd like my motors to match. Let me know what you think.

    the thing I ran into was that with the 1.75 ratio and 6150 limiter, you have to run a pretty tall prop to get good speeds. However, apparently hydrotec can raise the limiter now with a reflash.

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  4. #3
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    The engine has a velocity stack unit on it. But I may be interested in the Hydro-Tech carbon reeds and cut cages.

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    Strong engines. Im bumping the limiter this spring on mine. Mines a stage 3 with all the goods. Runs nice and cool. No issues. Great engines
    16ft superboat
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    15ft viper
    24ft sleekcraft
    21ft sleekcraft modvp
    18ft action hst drag
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    18ft vking yt 300 yamaha!


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