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  1. #1

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    '97 Speedster, cavitating

    My Speedster is cavitating from the holeshot. I replaced the wear rings not that long ago but it didn't fix the problem, what else would you folks suggest? I did notice that one of the drive shaft protectors was broken but not sure if those protectors effect cavitation.

    Thanks... A.


  2. #2
    crzyjetskr's Avatar
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    Aug 2010
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    Check the prop if it sucked a rock through it could be bent on the back side causing this.

  3. #3
    abarrassr07's Avatar
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    make sure carbon seal or boot is not letting water into the hull it will cause cavitation. on my xpl my pump shoe tunnel was not siliconed and it caused cavitation. and check your wear ring again. the only ones i buy is oem as every aftermarket wear ring ive tried was shredded after a few hours of use

  4. #4

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    Thanks, I'll pull the pumps this weekend and take a look. So those driveshaft protectors wouldn't affect cavitation?

  5. #5
    abarrassr07's Avatar
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    Quote Originally Posted by ubernoob View Post
    Thanks, I'll pull the pumps this weekend and take a look. So those driveshaft protectors wouldn't affect cavitation?
    if you are talking about the plastic piece around the shaft that screws on the back of the engine then no. i always rip mine off any way as when you ride it you cant see if the carbon seal is shooting water in the hull.

  6. #6

    Join Date
    May 2011
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    Take a look at these issues and see if they help. The jet boats do have some cavitation at a hard start just because there is so much more boat to get going. Is this cavitation new to you or has it always been there?This is from Group K.

    Pump Shoe - The pump shoe is the actual metal part (bolted to the hull) that the pump body seals up against. In the case of the 14.5's, the shoe and the ride plate are made as one piece. It is "fundamental" that this shoe/ride plate is perfectly sealed to the hull with a high-grade silicone sealer. Herein lies a lot of the cavitation problems experienced by many 14.5 owners. Many of these shoes came from the factory with breeches in the silicone that sealed them to the hull. On these units, no kind of custom prop, etc, can eliminate the cavitation. The pump shoe/ride plate "must" be removed and resealed using "Permitex 66c Industrial Clear Silicone" (available in auto parts stores). Removal of the pump shoe is difficult (usually done with a hydraulic jack between the plate and the rear swim step). Once off, all surfaces must be completely cleaned of the old sealer. It is impossible to over emphasize the absolute importance of have this area attended to. We recommend This procedure for "every" single motor 14.5.

    As added insurance to sealing between the pump shoe and pump case, we recommend a foam pump sealing-ring (available from the SD dealer). This inexpensive foam ring assures that there are no unknown gaps in the crucial sealing surface between the pump case and the pump shoe.

    Wear Ring - The wear ring is a removable Teflon plastic liner that the impeller spins within. In a perfect world, this ring has no grooves or gouges on its surface, and it fits closely to the impeller’s outside diameter. However there can be considerable cavitation if the wear ring is gouged or grooved (as can happen from digestion of rocks or branches). In addition to the cavitation, a damaged wear ring reduces pump efficiency in a way that can cause the engine to run a few 100 rpm higher than normal (for any given speed). The end result is reduced pump thrust, and reduced fuel range. If your wear ring is damaged in anyway, it’s cost effective to replace it...and then stay away from rocks.

    Drive shaft protector - The 14.5's come from the factory with a white plastic sheath that slips over the drive shaft. This free spinning sheath is intended to make it easier to remove ropes that might get wrapped around the drive shaft. Unfortunately, the forces of debris entering the pump often causes this protector to fracture and break apart, thus contributing to cavitation. We chose to cut this protector off at the front of the drive shaft (a small part of it must remain to seal the shaft), thus increasing the pump’s water intake area. At this same time we shortened our dock-lines to a length that would bake it impossible for them the wrap the drive shaft when tied to the cleats on the top deck.

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