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  1. #1

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    Best Max RPM for a 1390?

    I have heard that the big motors like a little less RPM than the stock motor. Has anyone tested and found out what the best peak RPM is for... say... a 1390 EFI without powervalves?

    Eric


  2. #2
    There are too many variables between combos to have a best rpm.. Dplates, style of porting, compression, squish, etc all seem to vary a little and make a difference where the motor is happiest.
    Mine always likes 7300 the best..

  3. #3

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    Interesting, Ross. Thank you for the input. Do you find the ski flashing to a particular RPM and then slowly crawling up to 7300?

    I discovered that I was .5 MPH faster at 7080 RPM versus 7110 RPM, so I've started to wonder...

    Eric

  4. #4
    flyboy's Avatar
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    they like to rev, try to get around 7250-7300, like Ross said

  5. #5
    Quote Originally Posted by Gipper View Post
    Interesting, Ross. Thank you for the input. Do you find the ski flashing to a particular RPM and then slowly crawling up to 7300?

    I discovered that I was .5 MPH faster at 7080 RPM versus 7110 RPM, so I've started to wonder...

    Eric
    With my 7300 rpm prop, which was what i had in it on the 83mph passes, and at the bug, it is a rocket from 25mph up. Goes right up to 7300 in a snap, no slow crawling...

  6. #6
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    Quote Originally Posted by Gipper View Post
    I have heard that the big motors like a little less RPM than the stock motor. Has anyone tested and found out what the best peak RPM is for... say... a 1390 EFI without powervalves?

    Eric
    Hello Eric mine ran the fastest speeds at 7110-7100 rpm's.
    Like Ross said it depends how it's set up.

  7. #7
    good info

  8. #8

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    From what I've been told, the carbed 1390s love the RPM, whereas the EFI 1390s run a little better at lower RPMs as the EFI has trouble keeping up.

    Ross - are you running the 43 TBs on your 1390? That may be the answer.

    Eric

  9. #9
    Ross - are you running the 43 TBs on your 1390? That may be the answer.

    Sure am Eric, but thats not why, others have them and their setup doesnt like 7300 at all..

  10. #10
    WATER WOODY's Avatar
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    My 1390 EFI likes 7130rpm +/- ........7090 and under my ski will buck! 7160-7200 my speed goes down.MY setup on my ski peaks the torque out in the 7130 range.Every ski is not the same and requires alot of test and tune time to find out what YOUR ski likes.Dont go by what everyone else does,tune your own ski to see what it wants.

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