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  1. #1
    Rebcammaz's Avatar
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    I wana go faster, But i need help!

    Dear Hulk,
    My project 2003 Genesis I 1200 fuel injected started with a blown up ski i got for 500. When i took the motor apart, I found the crank had a bad bearing and a destroyed center piston and head. I went to SBT and got a new crank, gaskets and pistons (1mm over so now the bore is at 89mm). I had the cyls bored out and honed to 89mm each and i found a used head on ebay in good shape. While rebuilding, I also installed Boyseen reeds. Upon startup, it had no spark, so i sent the computer to DFI Technologies and they fixed it up and reset the hour meter. Initial runs found the engine to be great, but the ski was cavitating while going on plane, and running around 6600rpm with a top speed of 60.8 on the speedo so i got a 7.0 prop from NuJet. Still cavitates while going on to plane but it got a little better. Now rpms at 6500, top speed of 61 on speedo. I compounded, waxed and high buff waxed the bottom and still 6500 rpms and 61.2 on speedo. I got a baffeled waterbox from TDR racing and no change on rpms or speed. All tests were performed with me, my girl on the back, full 18 gal gas and full 6qts oil. My next step is a R&D intake grate to scoop the water in when going on plane to try and solve the cavitation. Does anyone know of other bolt on aftermarket parts for speed? Should i sell this ski and get a new one? BTW motor has 19.2 hours on it and runs great so +1 for SBT from me.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Be careful doing anything that alters the engine breathing on a Ficht fuel injected motor. Unlike many other fuel injected engines, the Ficht system does not monitor air flow into the engine.

    More air flow does not mean more fuel in a Ficht engine, and it does not produce more power, it just leans out the fuel:air ratio in the combustion chamber.

    Your maximum RPM seems low. My Virage TXi (same engine) reaches 6800-6900RPM sustained on smooth water. I would expect your Genesis i to do similar.

    At 6500RPM, you may be lugging the engine a little. If there is nothing reducing your maximum power output (compression?), then you may need less pitch in the impeller.

    The Genesis is a big hull, so you need a lot of blade area to grab the water, and modest pitch to allow the engine to rev.

  3. #3
    Plrs X45's Avatar
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    I have a Genesis FFI and the boat is so big it NEVER cavitates! This may be your problem. The intake grate will not make the boat faster. Although it may help hookup there shouldn't be a need for additional hookup with a hull that large and heavy.

  4. #4
    Plrs X45's Avatar
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    6 degree pump wedge yields 1mph too.

  5. #5
    Rebcammaz's Avatar
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    correction- the bores are 85mm now not 89mm. The 89mm is my 951 sea doo eng... BRAINFART

  6. #6
    Rebcammaz's Avatar
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    Quote Originally Posted by Plrs X45 View Post
    I have a Genesis FFI and the boat is so big it NEVER cavitates! This may be your problem. The intake grate will not make the boat faster. Although it may help hookup there shouldn't be a need for additional hookup with a hull that large and heavy.
    The only time it cavitates is when its going up on plane, than it is fine any other time... its only when taking off, either slow or punched out of the hole. Thats why i figured r&d's intake because it has a deep scoop to direct water in.

  7. #7
    Rebcammaz's Avatar
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    tomorrow i will check compression and report each cyl, as well as switch back to the stock prop and see what happens.

  8. #8
    Rebcammaz's Avatar
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    Quote Originally Posted by Plrs X45 View Post
    6 degree pump wedge yields 1mph too.
    who makes that wedge?

  9. #9
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Rebcammaz View Post
    The only time it cavitates is when its going up on plane, than it is fine any other time... its only when taking off, either slow or punched out of the hole. Thats why i figured r&d's intake because it has a deep scoop to direct water in.
    It might be jet pump ventilation, and not cavitation.

    If you have any air leaks forward of the impeller, the jet pump suction when the hull is moving slowly but under heavy power creates air bubbles in the water stream.

    As the hull picks up speed, the water in the intake to the jet pump becomes pressurized instead of suction, and any air leaks change into water leaks going out (which are hard to see when the machine is running, of course).

    Check the seams in the jet pump extension (wear ring) and pump base. The mating surfaces must be smooth and essentially air tight.

    Some guys use a sealant between the pump sections, others use anti-seize.

    The pump base must seal properly to the hull, and so forth.

    Also check the through-hull drive shaft seals. They can also leak air if they are worn.

    When you launch from standstill, the jet pump has water around the outside of the pump, so a pump intake leak can be masked by the surrounding water. As you accelerate the water above the ride plate empties out, and the jet pump exterior is now fully exposed to the air. Until you build up forward speed, the pump can ventilate.

  10. #10
    casey67's Avatar
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    Are you using a Solas impeller?

    The Solas would not work well with my 1050. It might make tuning simpilar with Skat Trak or Nujet(factory) Skat trak makes a great variety of impellers and I found 1 that works great for my application.

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