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  1. #1

    My first watercraft... 2007 speedster 150 SCIC

    Hello all... last weekend I bought my first boat and wanted to say thanks to all the knowledge shared on this site. I knew what to look for so that I could buy a boat that hadn't already blown the SC clutch, and knew what I needed to take care of after I got it home.

    I took a 2 hour test drive with the seller, noted RPM's locked in at 6900-7000 and GPS speed at 49-51 MPH on less than perfect water. The seller allowed me to pull the intake tube and check that the SC impeller was not spinning freely. All seemed in good gondition so I bought it. It had 39 hours on it after my test drive.

    Currently putting the SC back together after a full rebuild (still had the ceramics ) and am aiming for the 110 in-lbs breakaway mark using McMaster washers. When I took it out, breakaway was at 60 in-lbs. Do you guys feel that this could be contributing to the lower than expected RPM's or is that just purely due to my altitude/temperature (~5500 feet/95 degrees)?

    Once again thanks for arming me with the knowledge shared on this forum.


  2. #2

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    Although 60lbs slip is low and should be tightened up like you're doing, looking at your altitude and temp, I'm betting that's the problem. I just got back from Colorado, and saw first-hand the huge performance hit to our cars and ATVs. You know, I've never heard anyone mention this, but it seems to me at that altitude, you should be able to throw on a X-charger, with no other mods, and be able to pump in enough air to make it perform more like it was at sea level.

    Me, I'm trying to make mine perform more like it's falling from outer space. My head goes in for porting next week, and a Riva ECU will go in after that. Too many mods going in right now to keep up with.

    If you don't want to upgrade your supercharger, you'll end up having to depitch your prop or get a new one. A Solas 13/18 will accelerate much faster than the stock prop, and should raise your max RPM by a couple hundred. The SC is barely producing boost at 7000, you gotta get those RPMs up another thou.

    Congrats!

  3. #3

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    I definitely loose about 300 rpm at an altitude of about 3600 ft. So loosing 500 RPMS at 5500 ft seems reasonable.

  4. #4
    Quote Originally Posted by VX1 View Post
    Although 60lbs slip is low and should be tightened up like you're doing, looking at your altitude and temp, I'm betting that's the problem. I just got back from Colorado, and saw first-hand the huge performance hit to our cars and ATVs. You know, I've never heard anyone mention this, but it seems to me at that altitude, you should be able to throw on a X-charger, with no other mods, and be able to pump in enough air to make it perform more like it was at sea level.
    I'm in Colorado at 5400' ASL. Altitude is THE reason I've got a turbo on my car and supercharger on my boat. You really need forced induction to replace some of the lost atmosphere. To your point, I think an un-tuned un-supported x-charger at my altitude would be just fine also. Consider that my atmospheric pressure hovers around 12.0-12.1. Compare that to 14.7 for sea level. With my stock charger at same boost as sea level guys, my engine sees 2.7psi less boost. How much more boost does the x-charger run vs. the stock charger? If the difference is 3-4psi or less, I should easily be able to run an x-charger without other mods and see a good gain.

    On my local lakes I can't get much above 7520rpms. I took the boat to Lake Powell (UT) earlier this year and also to Lake McConaughy (NE) and was able to hit 7700-7720rpms at those lakes (but they are also much larger and can have much calmer water).

  5. #5
    I finally got the boat out yesterday after rebuilding the SC.... and the performance was not affected at all, so obviously the low slip moment on the clutch was not causing the SC to slip. Overall the boat runs great, but I would like it to run as good as it was intended. Given my altitude, I'm wondering if the Riva genII impeller would be a good investment, seeing as it provides around 2 PSI over the stock SC impeller?

    I guess I need to eliminate all other sources that could be limiting my RPM, right now the SC is fresh, engine has new plugs, and the oil level is set correctly. Seeing some other posters say they get closer to 7500 RPM at my altitude makes me wonder if I am missing something. Any suggestions appreciated.

    Guy on the water, what lakes are you running on in Colorado? I've mostly just been running on Horsetooth.

  6. #6

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    You might find that you can sell your stock SC and get the "X", for less than you can get the drop-in wheel for. I've been through just about all the superchargers; my first was a drop-in, and I really wasn't impressed. You'll barely feel it on a heavy boat, especially with your altitude issue.

  7. #7
    Quote Originally Posted by Lunchbox View Post
    Guy on the water, what lakes are you running on in Colorado? I've mostly just been running on Horsetooth.
    Unfortunately the lakes in Colorado aren't great. We did a Lake Powell trip in June and just got back from a trip to Lake McConaughy (3 hrs from Denver in Nebraska). Both amazing lakes. McConaughy best beaches anywhere. For quick little local trips we do Chatfield or Cherry Creek. I've got to have a great beach, and both of those places are okay. Those are both 30+ minutes for us though... sometimes we will do Horsetooth but not this year.. Carter is terrible. Dillon is a nice scenic lake but we have more fun at Green Mountain Reservoir.

  8. #8
    Great, thanks for the input. I think I may just throw the x-charger at it this winter. I did some reading and have come to the conclusion that all the moving parts are the same between the stock SC and the x-charger (other than the impeller), is this right?

    Do you think I will be OK sticking with the stock injectors at my altitude, or are there circumstances where I could end up running too lean if I don't change out to the 42# injectors?

    Thanks guys

  9. #9
    ^^ I am probably doing the exact same thing. Since our Patm is 12.0-12.1 and sea level is 14.7, our engines see ~2.7psi less boost. So, I feel that if the increase in psi going from stock to x-charger is less than 3psi, then us high altitude guys ought to be able to easily make this change with no other mods and more or less have our x-charged boat perform like a stock boat at sea level. The key question is what is the delta psi between stock and x-charger? Should be easy to find on here but I haven't looked for it yet. I guess I'm repeating myself from an earlier post.. but still don't think we need any supporting mods to run an x-charger.

  10. #10
    MSRXP's Avatar
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    That charger needs to be set at 110-120 inch lbs. That is a definite reason for RPM loss....

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