jet drive trouble please help?

Discussion in 'Jet Drives' started by lozzfish, Aug 2, 2019.

  1. lozzfish
    Joined: Aug 2019
    Posts: 4
    Likes: 0, Points: 1
    Location: Swansea uk

    lozzfish New Member

    I have recently purchased a Wilson flyer dory with a Ford 1800 diesel engine and jet drive. Think it's a pp but not sure? The engine runs very well but the boat seems very low on speed only 7/8 knotts at 4200 revs?
    I was told by the owner the boat will cruise at 15/20 knotts? Please can any one shed some knowledge and expertise to help me? photos attached of boat engine a jet drive.
     

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  2. KeithO
    Joined: Jul 2019
    Posts: 112
    Likes: 11, Points: 18
    Location: Michigan

    KeithO Senior Member

    Assuming that it worked at one time ??? A free reving engine coupled with not much boat speed suggests that the jet pump is worn out. A working jet pump will absorb a lot of power and load down the engine and by pumping a lot of water, it should also have a lot of thrust.

    So if you have already checked the intake and are sure that nothing has been ingested into the jet pump and also that nothing is wrapped around the core of the pump rotor, then usually it means that the rotor/housing clearance is too large.

    Because of the fact that there are usually no exposed parts of the drive and also no rudder, jet boats are subject to the most terrible abuse. People will drive them up beaches, through shallow water on the plane that is only a few inches deep etc etc. The first jet boat that I bought came with a motor that was seized and I discovered why it was seized when I disassembled the engine (which was beyond repair) and found all the cooling passages filled with sand and gravel. The boat had been run in the shallows far too often and the slurry consisting of water gravel and rocks passed through the pump, which tore it up, and the smaller stuff made it from the pump into the engine block and then couldn't make it back out again...

    So not knowing your pump model, you will have to determine how wear is taken into account. A lot of the modern watercraft (jetskis) have a sacrificial liner on the inside of the pump which is fairly easily changed out for a new one, or even an undersize one if your rotor has to be skimmed on the OD to "true it up". The leading edge of the rotor which is facing the intake may also be in a bad way from rocks and gravel. If you dont have a sacrificial liner, you may have to get a new housing and rotor and install them as a set. Sometimes you can get a prop repair place to weld up the rotor to make up for missing material and then skim it down to a diameter that matches the housing ID after that has been cleaned up on a lathe. The parts for the Mercury jet drive that I had were very expensive to buy and that was the route that I took to get performance back to something approaching "reasonable" which translated to a fuel consumption of about 10-12 gal/hour. After I got rid of that boat (with a brand new powerhead) I got a similar size runabout of the same length with a regular outboard motor of the same (prop) hp and it used 1/3 of the fuel and had much more positive control at speed and deceleration when you come off the throttle with the lower unit in the water vs the jet drive. But then I dont have any special needs, which may dictate a jet drive over any of the alternates...
     
  3. baeckmo
    Joined: Jun 2009
    Posts: 1,112
    Likes: 116, Points: 63, Legacy Rep: 1165
    Location: Sweden

    baeckmo Hydrodynamics

    Naah, that is not a PP jet, they have another nozzle arrangement. Would be fine with a few pics showing the inlet opening with the grating. First, check that the reverse bucket is not disturbing the outflow in its forward position. Then open the cleaning lid (engine off!!!) and check if there is any debris attached to the impeller vanes or to the inlet grating. Also check jet unit attachment to hull; there must be no way air can seep int the inlet duct.

    If nothing fishy there, you have to unbolt the stator (the "bowl" onto which the nozzle and the deflector are mounted) from the unit. Check for debris in the stator channels and eventual damage to stator vanes and tip clearance between impeller vanes and housing. More pics....!
     
  4. lozzfish
    Joined: Aug 2019
    Posts: 4
    Likes: 0, Points: 1
    Location: Swansea uk

    lozzfish New Member

    What type of jet drive is it? Where can I get parts?
     

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  5. anthony goodson
    Joined: Mar 2007
    Posts: 422
    Likes: 17, Points: 18, Legacy Rep: 256
    Location: Dorset UK & Murcia Spain

    anthony goodson Senior Member

    Good afternoon baeckmo looks like a very early 65 to me ,which has been much molested.
     
  6. BlueBell
    Joined: May 2017
    Posts: 782
    Likes: 82, Points: 28
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Assuming you untied from the dock, follow Baeckmo's advice.
     
  7. lozzfish
    Joined: Aug 2019
    Posts: 4
    Likes: 0, Points: 1
    Location: Swansea uk

    lozzfish New Member

    How do you get the impella off do I need a puller. also where can I get a new impella from?
     

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  8. lozzfish
    Joined: Aug 2019
    Posts: 4
    Likes: 0, Points: 1
    Location: Swansea uk

    lozzfish New Member

    Where can I get the parts from? Thanks
     

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  9. KeithO
    Joined: Jul 2019
    Posts: 112
    Likes: 11, Points: 18
    Location: Michigan

    KeithO Senior Member

    Apparently the boats are still being produced. There is a Facebook page by the new owner Garry Bull. "Wilson Flyer boats". There is a phone number listed 0796 787 2423 garrybull@btinternet.com
     
  10. baeckmo
    Joined: Jun 2009
    Posts: 1,112
    Likes: 116, Points: 63, Legacy Rep: 1165
    Location: Sweden

    baeckmo Hydrodynamics

    Hi Anthony, nice to see your traces here. You are probably right about the origin; I did not get in touch with the old 65-s. From the later pics sent by the owner, it does look very much pp-ish. Can't see what the transition between hull and inlet duct looks like, though.

    Now to lozzfish: you don't need any puller to get the impeller off. You use the threaded holes in the impeller hub to extract the impeller. But be very careful: when all three screws are in contact with the nylon bushing, turn the three screws in small increments (max 1/6 of a turn at a time) and equally for all three.

    From the pictures it can be seen that there is damage to at least one stator vane, when you get the impeller off, please give us a few pics of the inlet side of the impeller and the inlet side of the stator. A picture showing the inlet opening in the hull bottom might be useful as well. Next questions: What is the power/rpms of the engine and do you have any idea of the boat weight?

    And don't worry about parts until you know if there is need for replacement; Anthony Goodson knows these jets better than anyone else here, he may come up with some advice when we found the reason for lack of thrust.
     

  11. anthony goodson
    Joined: Mar 2007
    Posts: 422
    Likes: 17, Points: 18, Legacy Rep: 256
    Location: Dorset UK & Murcia Spain

    anthony goodson Senior Member

    You will probably find the three threaded holes in the polyacetal bush are stripped, in which case the best way to remove the impeller is to loosen the three bolts in the polyacetal bush and then place a block of wood on the rim of the impeller boss, ie where the balance holes are, and hit it forward with a lump hammer.The impeller will shift forward off the polyacetal bush ,and can be pulled back by hand with the bush, sometimes a screwdriver gently in the slit in the bush helps with withdrawal. Wilson at this time made a 17 ft a 20ft and a 23ft I am assuming from the picture that this is a 20 if so with that engine and jet it will weigh over a ton ,which is too heavy for that jet to ever be efficient.
     
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