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Thread: Riverjet Version 1 reliability modifications

  1. #1
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    Default Riverjet Version 1 reliability modifications

    Picked up a brand new Riverjet locally for $150. That was a steal I couldn't pass up. It's the first version, so it has all of the flaws. Fortunately, the jet boat enthusiasts have all sorts of well documented threads with lots of upgrades, improvements, and changes to follow. For the most part, everything I've done here was already documented by someone else. I just followed the pictures and bought the parts.
    2019-02-17 17.41.14.jpg

    After I tore everything apart, the first step was to reinforced the thin spots at the rear of the hull with dyed epoxy. Horizon modified the mold and manufacturing process so that the new hulls aren't stretched as thin at the rear strake ends and floor to transom transition. I didn't have any holes in my hull, but the ABS was incredibly thin and easily seen when held up against the light. Problem solved.
    2019-02-17 17.40.08.jpg 2019-02-17 17.40.20.jpg

    I drilled the pump housing for a stuffing tube grease port to greatly simplify maintenance between runs. This modification has been done on jet pumps for a long time and was an easy mod once everything was pulled apart. Now there's need to pull any parts just to regrease the shaft after each run. The hole is filled with a small hex grub screw that threads into the pump housing plastic. Pull it out, inject fresh grease with a grease gun, then screw it back in to place. Much easier than the method Proboat had intended users follow with the stock setup.
    2019-02-17 17.40.40.jpg

    I ordered an updated impeller from Horizon. The original design had a 90* angle between the blades and hub body and was prone to crack. The revised impeller has more of a radius curve with more material where the blade meets the hub. I cleaned up a little flash with my Xacto knife along the edges and it dropped right onto the stock shaft.
    2019-02-18 10.54.02.jpg
    Last edited by fweasel; 02-18-2019 at 11:09 PM.
    Vac-U-Tug Jr (13mph)

  2. #2
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    I modified the rear stator to support the shaft with a proper sealed bearing. The stock brace that supports the end of the stuffing tube inside the pump housing has been known to crack, sending the impeller into the pump housing and to an early death. The stock brace gets cut out of the pump housing with an Xacto blade and tossed in the garbage. The gape around the stuffing tube where it passes through the pump housing needs to be sealed and water tight. I used CA glue and Zap kicker. The rest of this is done with the stator that fits into the rear nozzle housing. A plastic washer and brass bushing get pressed into the stator first and serve as spacers to position the bearing at the proper depth. The lock nut on the impeller rests perfectly inside the bearing and positions the impeller at the proper depth in the pump housing. I had to try three different lock nuts before I found one that worked. The first was too large and wouldn't slip into the bearing. The second one fit, but wasn't true, which caused a wobble in the impeller. Last one was the winner. No intricate adjustments needed when reinstalling as the impeller presses right up against the bearing.
    2019-02-18 10.55.20.jpg 2019-02-18 10.58.10.jpg

    I chose to replace the stock nozzle with a modified 3D printed version. Several people installed inserts into the original nozzle and reported more accurate steering response. The stock nozzle has been reported to provide a vague steering near the neutral position which makes tracking straight difficult. I never acutally ran the boat in stock form, but the complaint was heard often enough that I wanted to make the change. A complete nozzle with a narrower diameter seemed like the best solution to me. The designer of the modified nozzle went through several versions before settling on this design. You can see that it easily fits inside of the original, showing the difference in size between the two. The exterior dimensions are all the same and it bolts right into place with only a little lite filing on the pivot holes to keep it moving freely. Got everything mounted back on the hull and dialed in. I flipped the rubber push rod boots to the inside of the hull to clean up the rear of the boat. I might try dying the new nozzle with orange fabric dye. Years ago when I was a kid, I used to dye the white nylon parts from my Associated RC12 carpet racer with RIT fabric dye in a pot of boiling water. Not sure what material the 3D printer used, and if it will absorb the dye or not. Thought it might look cool, worth a try.
    2019-02-18 10.41.02.jpg 2019-02-18 10.41.13.jpg 2019-02-18 12.29.26.jpg
    Last edited by fweasel; 02-18-2019 at 11:18 PM.
    Vac-U-Tug Jr (13mph)

  3. #3
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    Following Rafael Lopez's lead, I replaced the flywheel coupler with a standard brass 4mm to 5mm brass coupler. I don't need the self-righting feature and prefer the performance gain from a lighter drive train with less hull lean. As long as the stock outrunner motor doesn't start throwing magnets, I should be good to go. If that happens, I'll switch to an inrunner motor and water jacket.
    2019-02-18 10.55.48.jpg

    I installed a Spektrum micro servo to be able to adjust the nozzle trim. I plan on creating a steering mix in my transmitter to keep the trim neutral while tracking straight, and then slowly trim positive when turning left/right to help raise the bow of the boat. I needed a 3ch receiver, so a spare 4ch will work just fine. Took the receiver apart and coated it in epoxy to fully water proof it first
    2019-02-18 20.54.40.jpg 2019-02-18 20.53.54.jpg
    Last edited by fweasel; 02-18-2019 at 11:21 PM.
    Vac-U-Tug Jr (13mph)

  4. #4
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    The last couple of things I'm working on are the cooling lines and water pickup. I had some orange 4mm hose that matches the stock colors perfectly. Rather than enlarge the hole in the transom to fit the oversized tubing, I installed a threaded bulkhead fitting. I hadn't intended on altering the water pickup, but the size of the barbed fitting is a little too small for the new cooling line. I have a larger diameter fitting, but it's not long enough to protrude down into the water stream inside the housing. I need to order a piece of 3mm K&S brass tube and cut a small piece to insert into my larger barbed fitting. I'll solder it in place and file the edge into a pointed tip like the stock pick-up. I would have been done with that, but the smallest brass tube I had on hand was just a hair under 4mm in diameter.
    2019-02-18 20.52.28-1.jpg 2019-02-18 20.52.09.jpg 2019-02-18 20.53.37.jpg
    Vac-U-Tug Jr (13mph)

  5. #5
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    Built a new, larger pick-up with a threaded barb and small piece of KnS brass tube. Soldered the two pieces together and filed a tapered edge to match the stock pickup. I drilled out the hole in the nozzle housing, cut new threads, and screwed in the new piece. Now the 4mm tubing fits very snug, no need for a zip tie.

    2019-02-21 19.48.15.jpg 2019-02-21 20.03.42.jpg
    Vac-U-Tug Jr (13mph)

  6. #6
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    Replaced the stock hatch screws with a set of spring loaded hatch locks. They were a bit short, but fit and work much easier than the stock screws.

    2019-02-20 16.52.48.jpg 2019-02-21 21.16.38.jpg 2019-02-21 21.18.38.jpg
    Vac-U-Tug Jr (13mph)

  7. #7
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    Nice. I love the jet boat.! Will do another one day. That propulsion unit looks a lot better than the NQD ones. Lol

  8. #8
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    Quote Originally Posted by srislash View Post
    Nice. I love the jet boat.! Will do another one day. That propulsion unit looks a lot better than the NQD ones. Lol
    I think it is, especially after you make a handful of cheap fixes. The new TFL unit looks awesome, but it ain't cheap.
    Vac-U-Tug Jr (13mph)

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