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  1. #1
    Trent_sl750's Avatar
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    1995 sl750 top speed

    My sl750 will only reach about 43-44 on glassy water at 6350rpm. Good compression all across. 160ib rider, my buddy in his little 1994 yamaha vxr pro 701cc can almost keep up and hes 200ibs!

    Is this the right speed? Seems a little slow to me!


  2. #2
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    They should run about 48. I would check out the jet pump/impeller. RPMs are there speed isnt. My guess is worn impeller or stator damage or both.

  3. #3
    Trent_sl750's Avatar
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    I guess i will check the clearance between the impeller and wear ring to start.

    iv also been reading that sealing the intake grate and ride plate can also help a little, but im not sure how that would help or where i would need to seal?

    Does sealing really help anything?

    thanks!

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Trent_sl750 View Post
    ... I've also been reading that sealing the intake grate and ride plate can also help a little, but im not sure how that would help or where i would need to seal?

    Does sealing really help anything?

    ...
    Yes, the jet pump and ride plate must be properly sealed.

    Incorrect sealing or missing sealant can allow the jet pump to draw in air bubbles instead of just water. Ingesting air will reduce the jet pump thrust, especially when accelerating from low speeds.

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  6. #5
    Trent_sl750's Avatar
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    So just pull the jet pump off and put some silicone where it mounts up to the hull, and then where the grate meets the hull too?

    So i could possible gain a mph or two doing this?

  7. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Trent_sl750 View Post
    So just pull the jet pump off and put some silicone where it mounts up to the hull, and then where the grate meets the hull too?

    So i could possible gain a mph or two doing this?
    Mostly the sealing is needed around the front edges and sides of the ride plate, plus where the pump base meets the transom and the pump shoe. Also where the intake grate slots into the ride plate.

    The sealant should be something than can stay put in a marine environment.

  8. #7
    Trent_sl750's Avatar
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    Click image for larger version. 

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ID:	334176Update:

    impeller has less than .015 gap, but two of vanes on the stator have big plugs taken out of them, could this be any off the speed loss im seeing?
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  9. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Trent_sl750 View Post
    Click image for larger version. 

Name:	image.jpg 
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ID:	334176

    Update:

    impeller has less than .015 gap, but two of vanes on the stator have big plugs taken out of them, could this be any off the speed loss im seeing?
    That impeller is quite beat up. Lots of dings and unevenness to the leading and trailing edges. This will induce cavitation, which can burn metal away.

    I would look to having that impeller refurbished or replaced.

    The damaged aluminum stator vanes are not helping, obviously. If you can find a stainless steel six vane stator that would also improve thrust, especially combined with a good condition impeller.

  10. #9
    RLACEMAN's Avatar
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    Between the chunks out of the stator assembly & the dings on the leading edges of the impeller, this is where you are losing a good 3 or 4 mph.

    I have a very low hour replacement stator 5 vane aluminum like you have with a used 13/18 skat-trak swirl impeller attached, this impeller will perform better than the stock one if it was in new condition, & the hole shot compared to stock is a great improvement, & top speed is a good 1 mph over stock too.

    You should be able to just hit 50mph with this impeller. PM me if interested.
    Last edited by K447; 06-28-2014 at 01:48 PM.

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