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Thread: Slow 15X

  1. #1

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    Slow 15X

    Sold my old F15X to a mate with 50 hours and purchased a new 08 15X. Problem is, the new ski is significantly slower than the one it replaced. Engine speed in water is 6300 rpm vs the old ski's 6500 rpm. Jumps me out of the hole and continues pulling way.. Bruce from Rising Sun Honda suggested to check boost pressure first. Where do you tee in to on the 1.5? Fuel Pressure regulator line?
    Anything else I should check for? Compression?
    Should I take it back to the dealer for repair? I know it sounds trivial, but it is kinda annoying!
    Help would be appreciated...


  2. #2
    Both mine, and my mates F-15X's turn at 6400RPM; pretty much dead on, on flat water... this drops slightly once you've been running at WOT for a while and heatsoak starts to effect the intercooler.

    Have you GPS'ed both? Is it possible that more wear in the old ski's pump was allowing the impeller to spin a smidge faster?

  3. #3

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    Quote Originally Posted by Desty View Post
    Both mine, and my mates F-15X's turn at 6400RPM; pretty much dead on, on flat water... this drops slightly once you've been running at WOT for a while and heatsoak starts to effect the intercooler.

    Have you GPS'ed both? Is it possible that more wear in the old ski's pump was allowing the impeller to spin a smidge faster?
    Was thinking about swapping pumps over to see what difference that made, but the older ski always revved to 6500+ rpm, but also cavitated a little too. Would have thought if the pump was worn causing higher rpm, it would be slower?
    Haven't GPS, but it is obvious what one is faster in the water when it flies by.

  4. #4

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    remove all snake hoses in compartment, install 3-4'' air intake intstead of stock 2'', if use stock air intake, take out air filter , cut/file 2 outside bar w/wind on intake grate, fill all ride plate,intake grate nut holes w/silicone, remove screen inside stock intercooler, add 2.5degree wedge ring for ocean ride, 5 degree for river or use sander to sand your ride plate. adjust rear seat higher, take out tray and rear seat rubble seal so hot air can escape. I used 5 degree wedge for river, I run solid 67-68mph. Now I have Mac stage II kit, now run solid 74mph. Rudy at R RATED is testing bigger turbo, will know the result next week. Hope this help


    Quote Originally Posted by hondaturboboy View Post
    Sold my old F15X to a mate with 50 hours and purchased a new 08 15X. Problem is, the new ski is significantly slower than the one it replaced. Engine speed in water is 6300 rpm vs the old ski's 6500 rpm. Jumps me out of the hole and continues pulling way.. Bruce from Rising Sun Honda suggested to check boost pressure first. Where do you tee in to on the 1.5? Fuel Pressure regulator line?
    Anything else I should check for? Compression?
    Should I take it back to the dealer for repair? I know it sounds trivial, but it is kinda annoying!
    Help would be appreciated...

  5. #5
    Dave Sharp dav_dman's Avatar
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    Quote Originally Posted by hondaturboboy View Post
    Was thinking about swapping pumps over to see what difference that made, but the older ski always revved to 6500+ rpm, but also cavitated a little too. Would have thought if the pump was worn causing higher rpm, it would be slower?
    Haven't GPS, but it is obvious what one is faster in the water when it flies by.

    subscribed. Will be interesting to find out what this is. Keep us posted pls?

  6. #6
    Dave Sharp dav_dman's Avatar
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    Quote Originally Posted by hondaturboboy View Post
    . Where do you tee in to on the 1.5? Fuel Pressure regulator line?
    your stock fpr is boost sensitive? Has a boost line connected to it?

  7. #7

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    Going to check boost pressures on both skis this weekend. Phoned a couple of dealers and they tell me in water rpm is around 6350 - 6400 rpm. Don't know why the older ski is faster on the water and rpm wise. 6400 and slowly builds to 6520 rpm. Freak engine! Interestingly it also pulls away from my R12x with full stage II macsboost! Regretting my new purchase.

  8. #8

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    my f15x was doing 6530 rpm solid all day long, top speed 66.9 mph . 6350 rpm is correct with restricted stock air. Go with Mac f15x stage II or contact R RATED you will surprise with your 15f .


    Quote Originally Posted by hondaturboboy View Post
    Going to check boost pressures on both skis this weekend. Phoned a couple of dealers and they tell me in water rpm is around 6350 - 6400 rpm. Don't know why the older ski is faster on the water and rpm wise. 6400 and slowly builds to 6520 rpm. Freak engine! Interestingly it also pulls away from my R12x with full stage II macsboost! Regretting my new purchase.

  9. #9
    Quote Originally Posted by XRIDER View Post
    remove all snake hoses in compartment, install 3-4'' air intake intstead of stock 2'', if use stock air intake, take out air filter , cut/file 2 outside bar w/wind on intake grate, fill all ride plate,intake grate nut holes w/silicone, remove screen inside stock intercooler, add 2.5degree wedge ring for ocean ride, 5 degree for river or use sander to sand your ride plate. adjust rear seat higher, take out tray and rear seat rubble seal so hot air can escape. I used 5 degree wedge for river, I run solid 67-68mph. Now I have Mac stage II kit, now run solid 74mph. Rudy at R RATED is testing bigger turbo, will know the result next week. Hope this help
    Xrider, great info. I own a 08f15x gpscape and its a fantastic ski. How did you remove the screen from the stock intercooler?

  10. #10

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    take out your intercooler, you will need to unsrew 4 small hex nuts on the intercooler hose adapter then remove 3 screens, the middle screen you need to cut it off, use air clean/ blow off well on broken particle from remove the screen.


    Quote Originally Posted by Jetscape View Post
    Xrider, great info. I own a 08f15x gpscape and its a fantastic ski. How did you remove the screen from the stock intercooler?

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