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Thread: Help with Jet Boat

  1. #1

    Default Help with Jet Boat

    Bought a jet boat and am starting to explore with it and am making all sorts of newbie mistakes I guess.

    I freely admit I don't know what I'm doing but I wonder why the guys I took it to the first time it broke didn't explain to me what I'm doing wrong, maybe you all can help more than the shop I won't mention.

    On the Copper River this summer I had a bit of an adventure, in the course of which I sucked up a bunch of gravel on several occasions, cleared the grate and kept going. In the end the controls got stuck in reverse and we almost went down the canyon which would have been bad (understatement I know). the boat was also running REAL slow

    fast forward $1000, new controls etc.

    Last night on the 20 mile here were the symptoms:
    1) Got stuck and sucked up gravel. Cleared it all out of the grate.
    2) Brand new controls VERY hard to shift, I thought they were going to break again.
    3) Virtually no thrust. Noticed gravel not in the grate but clogging the area where the jet water EXITS the motor. I wasn't able to pull this gravel out but had to push it back in (Where does it go?)
    4) Low RPMS again (3500), low thrust.
    5) If I'd try to throttle up I'd gain speed then THUMP....loose all thrust. Throw it in reverse (with the scarily sticky controls) and gain some thrust till it happened again. The grate was clear and I was done sucking up gravel at this point in the evening Limped back to the boat launch as it got quite dark.

    What obvious bits of Jet Boating knowledge am I missing here. Understand that the boat just got out of the shop and should be running fine.......and it did until I hit the first sandbar. I thought running aground with a jet was par for the course from time to time.... you turned of the motor quick, cleared the grate and moved on from there. What could be causing these symptoms with the controls?? If they are bad I want to take them back right away.

  2. #2
    Member alaskanmoosehunter's Avatar
    Join Date
    Apr 2007
    Next to my trashy neighbor


    I had a problem like that a while back.

    This was my problem, could be yours.....or maybe not.

    I put newer controls in and I would open her (BOAT) up and lose of thrust. Not RPM's just thrust out of the pump.

    It ended up being that the reverse gate was not properly adjusted after the new controls where put in.
    (In your case something might be bent...Linkage, gate arm....???)

    The boat would power up until the resistance in the water was great enough to partially put the reverse gate in to the water flow from the jet unit....once the water flow was in the reverse gate the only way to get it out of reverse was to throttle back down and to neutral and start all over again until I could hobble to shore and fix the problem. Which at that time was to completely remove the reverse gate and enjoy the rest of the day and work on the problem later.

    Good luck

  3. #3

    Arrow Thanks


    this all makes perfect sense. I'll look into the issues with the reverse gate tonight as I guess this must be causing the problem. As for the gravel that was all they way past the impeller out by the jet output (We're talking about some BIG gravel here....I have no idea how it got past the impeller) any ideas how it got there and where it went when I pushed it back in? I suppose it eventually pushes it's way out?



  4. #4


    In general for a jet if your RPM increases then there is either a restriction in the the intake/grate or the impeller is worn. If your RPM will not increase to normal then there is a restriction in the exhaust/outlet of the pump causing to much backpressure. As for the rocks that you pushed back they fall back down into the pump body and then when you throttled up they got turned the right way and slid through the outlet, the other way they can get out is to fall back through the foot.

  5. #5
    Member Crumm's Avatar
    Join Date
    Apr 2006
    Fairbanks, AK


    What kind of pump, motor and controls?

  6. #6


    Not sure about the pump.....I assume the water pump is being referred to. I'll try and flush it out with fresh water tonight.

    -The Motor is a 2000 Honda 4 stroke BJ90 (I think), basically a 65HP jet that would be 90HP if it were a prop. It came from the factory as a jet.

    The controls are Honda Outboard Controls.

    hope that helps


  7. #7


    Make sure your throttle lever and cable are adjusted correctly. As the throttle pivots forward to open the throttles, it will eventually start moving the throttle BACK as the arch of the lever moves around full circle...

  8. #8


    Another possible cause is that some of the rocks lay in the reverse cup and when you go into reverse the rocks wedge themselves between the cup and the jet. It happens quite often when you use your boat as a gold dredge. Just remember to check for rocks laying in the cup when you clean the foot, also if your controls are sticking like that it is easier and quicker to shut off the engine and push the reverse bucket out of the way either with your hand or a paddle (used both myself)


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