Glastron GT150 jet boat build?

Discussion in 'Jet Drives' started by Matt Ashland, Aug 16, 2019 at 4:26 AM.

  1. Matt Ashland
    Joined: Friday
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    Location: Minnesota

    Matt Ashland New Member

    Hey guys brand new to the forum! So I recently acquired a Glastron GT150 and an old sea doo with a 720cc motor in it all for free... The GT150 is sadly in pretty tough shape so this is the only reason I’m pondering this... That motor in the ski is rated at 85hp with a fresh motor and thinking about building a jet boat out of this. So my question to you guys is do you think that’ll be enough? I know it won’t be no speed demon by any means but if it does 40-45mph I’ll be more than happy. From my understanding these glastrons are fairly light. Only about 250-300 more pounds than the ski. Although it has more drag obviously I wonder if a slightly more aggressive impeller would do the trick? Anyways if you guys can shed some light on this and some knowledge that would be great. Thanks a lot!
     
  2. KeithO
    Joined: Jul 2019
    Posts: 71
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    Location: Michigan

    KeithO Junior Member

    Its definitely possible to do. Remember that when looking at jet system power, an engine that produces 90hp in outboard format is good for 65hp in a jet configuration. That is certainly how my Mercury motor was rated. Its possible that the Rotax inline systems are more efficient without the bevel gears.

    The big benefit of the motor swap would be a huge reduction of weight on the rear of the boat. Those inboard/outboard systems are heavy. Having said that, I think that the fuel consumption will disappoint you. Those 2 strokes operated at WOT can really suck fuel. The 90hp merc jet boat would go through 12-15gal/hour. If you had a way to connect the jet pump to a modern lightweight 4 cylinder motor instead of the 2 stroke motor, that would change things quite a bit.

    There is a company on the south island of New Zealand who make jet drive powerplants using GM crate engines and they have developed their own watercooled exhaust manifolds for the Ecotec engines.
     
  3. KeithO
    Joined: Jul 2019
    Posts: 71
    Likes: 8, Points: 8
    Location: Michigan

    KeithO Junior Member


  4. Matt Ashland
    Joined: Friday
    Posts: 2
    Likes: 0, Points: 1
    Location: Minnesota

    Matt Ashland New Member

    Thats what I was thinking too but finding a salvageable 4-tec jet ski around here is next to impossible. Most guys want about as much for the motor and jet pump as the whole jet ski would cost... and I think it would be really sweet to run like a 305 or even a 4.3l with jet drive but the motor alone weighs as much as the boat. So if I went the jet drive route I’ll almost have to stick with a rotax 2t or something similar and just fab up like a 15 gallon tank out of aluminum and live with the fuel consumption. Most of the lakes around my area are fairly small and just big enough to go out for a little cruise. I just don’t want to go through all the headaches of making this work and only have a 30 mph jet boat... lol so I’m kind of stuck between a rock and a hard place on what to do.
     
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