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  1. #1

    2006 STX-15F Strange Tapping Noise

    Just picked up an 06 STX 15f a month ago. 165 hours run time, ran great at time of test run, as well as a the following week. I gently rinsed the motor area using salt away, changed the plugs for general maintenance, and did not run it for a week or two. In the mean time we got several rainstorms, it was properly covered and did not take on any water, but some dirt was able to splash up in the pump area. I gave it a quick hose down and off to the water. Got it off the trailer and upon starting it, noticed that it too way longer to start, and it did not seem like it was running on all cylinders. A strange tapping noise seemed to be coming from the pump area, but could not be certain thats what it was. After a quick jolt of the throttle, the noise went completely away and it thrusted forward, but not like normal, something didnt seem right, and the noise returned instantly again at idle. Motor seemed to run perfect after this incident but noise was persistent, immidiately back to the trailer! It starts up perfectly now on the trailer, but noise is no better. Nothing looks abnormal in the pump or housing, but I am really suspect of it. I am hoping to disassemble the pump and inspect, in the mean time any suggestions would be helpful, thanks!

  2. #2
    slothman's Avatar
    Join Date
    May 2011
    how loud is the tapping? Is it more of a knock? Hate to say it but could be a piston or valve. Do a compression test or a leak down test to see for sure.

  3. #3
    That sounds scary, but not the case, here is the update. My first issue was the way it ran, so I attacked that instantly and pulled the plugs after another long hard start. What I found was surprising! Cylinders 2 and 4 spark plugs were soaked! I put the old plugs in just to see if there was any difference, fired right up! No noises or anything, I did a quick inspect on the pump and found a slight rub mark on the wear ring, so I plan to fix the pump bearings and get a new wear ring in the near future. Just found it odd that the new plugs were faulty, and before I get new ones I plan on trying it again in the water with the old plugs just to ensure that I have isolated the problem.

  4. #4
    Pain is fear leaving your body.... rlovebk's Avatar
    Join Date
    Aug 2008
    So. Cal.
    1. Make sure you use anti-sieze on the plugs and ALWAYS torque to spec. (i think its 17lbs but check your manual as I could be wrong)

    2. ANYTIME you suspect your pump bearings are shot STOP the motor and get a tow. If your pump bearings go bad it can take your motor out by thrusting shaft against the crank. You can upgrade to the new 300X pump set up but it'll cost you about 300 just for the housing, plus other parts are needed. It is very rare for a 15 to eat it's motor from this but it has happened.

    3. Check your pump bearings every 50 hours. If all is good you just clean-up, load everything with waterproof grease, and you can re-use seals/bearings also if they are in good condition. I have re-used mine 4X now and they are fine.

    4. Check the tolerance of your prop/wear ring when you pull the pump. I think .18 is good. Again I am going by memory here so check your manual, but if your tolerance is tight then just very lightly clean your wear ring up with light sanding, but only if it is rough and you don't want to take it out of tolerance here. If it's whacked buy another. If it has alot of edges that stick up in the flow, etc, that can cause cavitation. Look for cavitation burns on your prop and that'll usually clue you in as to the condition of this. Look at your prop edges too.

    That is a weird thing about your plugs. Make sure when you run on hose its motor on, hose on, hose off, motor off ALWAYS.

    I have been using Dawn soap on mine for years and other skis also and it cleans it up good. Much less spendy than Salt-Away. The 15F run it about 5-10 minutes at idle on hose cleans it up good. Just blow out all you can on the waterbox.

    Great ski have fun on it! Good luck.

    There are lotsa folks on here that know much more than myself about these. Lot of good info on here.

  5. #5
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
    Join Date
    May 2008
    Sounds like it was flushed wrong, when I was experimenting with a straight exhaust I found that if there is any water that gets into the exhaust manifold it can get sucked up into the engine and give you wet plugs.


  6. #6
    Thank you for all this info, it is extremely useful! I read in another thread something about draining the intake, is that something I should consider doing just to be cautious since I am new to this ski? Is it hard to do? I was also wondering what is the best way to blow out the air box, run it on the trailer? and would it help at all to tip the trailer up a bit while doing so?

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