Jet Gheenoe question

Discussion in 'Boat Yard Basics' started by jladdsmith, Sep 17, 2011.

  1. jladdsmith

    jladdsmith I Love microskiff.com!

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    Guys,

    I can't believe this is my first post. I've been cruising Microskiff for years now.

    Anyway, I have a 13' Gheenoe and wanted to power it with a motor out of a Surfjet. This is probably a bad idea, but I already have two of these motors, and they are practically new.

    It's a 255cc 15hp Subaru motor. With the motor and pump, it weighs exactly 50 lbs.

    Assuming a 30% loss at the pump, this equates to 10.5hp. I know that I'd have to make a pad for the hull. My Gheenoe has low front decks and probably weighs in at 130lbs, or probably 145 with the pad, or about 160 with bottom coating such as lineX. The surfjet in it's standard form, including engine weighs about 130lbs.

    See this link for a description of the motor. http://www.deckjetwatercraft.com/surfjet/default.asp

    My guess is that this is a bad idea. What do you guys think?

    I'm just dying to use these motors in something.

    Thanks,

    Jonathan
     
  2. firecat1981

    firecat1981 BBA Counselor

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    The power would be fine, but the weight would be a bit much for a 13'r.

    Honestly I was going to say don't bother, because there were others that tried jetski motors and they didn't work very well, but being it's only 15hp I say go for it, whats the worst that happens, you ruined a gheenoe?
     

  3. noeettica

    noeettica Well-Known Member

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    Sounds Interesting PM me and I'll give you an E-Mail address


    Looking forward to build photos


    Thinking "outside the Box " Is Great !!!
     
  4. jladdsmith

    jladdsmith I Love microskiff.com!

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    I was thinking the opposite! This motor (with pump) weighs 50 lbs. An outboard in that range would weigh at least 25lbs more, right?

    I'm more concerned with the hull design really. From what I understand, I'd have to make a flat pad in the shape of a v that would extend three feet forward of the intake.

    My current Gheenoe has been modified with low decks and a seriously reinforced transom with lapped boards on the inside, new gelcoat, etc. Probably not the best 'noe to go cutting on in the case that this doesn't work. I think this one will need to stay as is, and find a beater for testing. There just aren't that many beaters in the TN area unfortunately.

    If anyone knows of a cheap cheap 13'er around here, that's an option.

    Separate question: How can I find the HIN for my boat?

    The guy who rebuilt it put a "big bow cap" extending about 2.5 feet back. This will be coming off. Anyway, the original aluminum Gheenoe cap does not have the HIN engraved on the underside. FWIW, I think this is an 83 model.
     
  5. DuckNut

    DuckNut Brandon, FL

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    May not necessarily be the case. You just want unaireated water. Once you get it mounted and get a pad made try it out. If you are sucking air flip the boat and make it longer. Easy to add a pad.

    As far as the HIN should be stamped along the top edge of the transom. Most likely whoever redid the transom did not keep it.
     
  6. firecat1981

    firecat1981 BBA Counselor

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    [quoteI was thinking the opposite! This motor (with pump) weighs 50 lbs. An outboard in that range would weigh at least 25lbs more, right?
    quote]

    I misread that, I thought for some reason you meant the 130lbs was for the motor and jet. At 50lbs it should be just fine. Curious, how much does one of these motors and jets cost? do you have any more info on it?

    As far as the pad goes, a gheenoe already has one of sorts. Just shave off the drain channel and give it a go. This will be an ongoing experiment, I would even try it as is first and see what happens.
     
  7. DuckNut

    DuckNut Brandon, FL

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    The hardest part of this experiment would be the placement and angle of discharge.
     
  8. noeettica

    noeettica Well-Known Member

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    There are a couple of "lowsiders" over on "customgheenoe"
     
  9. jladdsmith

    jladdsmith I Love microskiff.com!

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    Well, for now, it's going to have to be in planning mode as I just can't cut up my current Gheenoe. I need to find a beater.

    For more on the motor: http://www.pwctoday.com/f72/1984-surfjet-325298.html

    The manuals are also in the link from one of the other contributors to that thread.

    This guy has just gone through rebuilding one. He says the motor and pump weigh 65 lbs, though. I suppose this could be accurate as I weighed mine without the intake grate and bottom mounting plate. On the board (65lbs plus 90lb rider), he's getting 24mph at nearly 6k rpm. I don't think he's done the work to get the impeller shimmed tight enough. His board should have hit 30 mph.

    I agree that the mounting angle would be critical. As far as placement goes, as far aft as possible would be the only option really. You don't want to try and 'plumb' the output as it would dramatically affect performance. I would start with the discharge nozzle just below the waterline at rest and then adjust from there. Ideally, the discharge stream would be just above the waterline on plane.
     
  10. Chrysaora

    Chrysaora I Love microskiff.com!

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  11. tom_in_orl

    tom_in_orl Founder of Microskiff, Member of the Gheenoe Army

    Its been done several successfully several times before. You don't see a lot of them in Florida because most people are using their Gheenoe's in fairly shallow water and the jet motors have a tendency to get clogged. If you don't have that problem where you are at then it could be a great project.

    http://www.customgheenoe.com/forum/viewtopic.php?t=11113&sid=78aaaa3e2bb33f74f1c420baf3b521f6


    http://www.customgheenoe.com/forum/viewtopic.php?p=83116&sid=585936f7039abfbe75a0e38222a68151


    These were good threads but the posters didn't maintain maintain their pictures. Still there are some decent comments.

    http://www.customgheenoe.com/forum/viewtopic.php?t=2698&highlight=jetski

    http://www.customgheenoe.com/forum/viewtopic.php?t=2977&highlight=jet
     
  12. fsae99

    fsae99 I Love microskiff.com!

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    LOL, I just finished my monthly ebay/clist search for a deckjet to do just this. Although I only plan for 1 engine, just need something to get up river not, if I get 15 mph I'd be happy. The thing that attracted me to the surfjet was the packaging of the motor jet assembly.

    Johnathan, interested in selling one of the motors and pump?

    I really think a gheenoe could do without a delta pad. The triangle pad is used to flatten out a v shape to flow the max amount of un-aerated water.
     
  13. jladdsmith

    jladdsmith I Love microskiff.com!

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    Jim,

    I'm sorry that I didn't see this post sooner. I would be willing to sell one of the motors, but would make you a deal on both of them. One has a polished pump and needs a new seal on the impeller shaft. I have two brand new aluminum impellers as well as the zytel ones that came with them.

    We would just need to talk about it. Sending you a PM now.

    -Jonathan