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  1. #1
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    p2p adjustment for new prop

    I have swapped from a 24p tempest to a 25p and was wondering if there is a general rule of thumb for which way to move the jackplate to try and get more gains out of the top end. With the 24p I was hitting 65mph at 5600 rpm and with the 25p I hit 68mph and still had 5600 rpms(on vessel view). its a 200hp pro xs opti on a 10 inch manual jp, 18'8" cobra. Would like to see 70mph. prop to pad is roughly 3 3/8, driveway isn't super flat or level.

  2. Member
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    #2
    General rule is to raise the engine until your speed decreases or you start to lose water pressure. I had a Coral fish & ski with a 225 EFI with a 6" plate and just under 3 1/2" was the sweet spot. You're right there at 3 3/8". If it were mine I'd raise it up 1/4" and run it. Pay attention to your rpm, speed (gps), and water pressure. Usually what happens is your rpm may go up but you won't go any faster or you may even lose some speed. If that happens you're too high and have increased your prop slip. Just be sure and pay attention to your water pressure cause you can cook the engine in a heartbeat. Good luck. All in all I think 68 on a 18'8" hull is pretty good with a 200. The cobra hulls weren't exactly light weight go fast hulls.

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    #3
    My Cobra 180 DC with a 175 EFI loved a 4 blade Trophy Plus. Was faster than any Tempest I tried, I think due to the 4 blade lifting the stern some. If you can get your hands on one, it might be worth trying. Mine would run 67 with the Trophy.

  4. Member
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    #4
    raised the jackplate half an inch and lost 150 rmp and 2mph...lowered it back an 1/8th from where i started. I'm keeping my eyes out for a 4 bladed prop locally i can borrow.

  5. Member
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    #5
    Quote Originally Posted by Fishaholic Ty View Post
    raised the jackplate half an inch and lost 150 rmp and 2mph...lowered it back an 1/8th from where i started. I'm keeping my eyes out for a 4 bladed prop locally i can borrow.
    Been there and done that. I suggest you save your money on the 4 blade option. I have found that the Tempest Plus has been the fastest and best lifting prop on my last three boats (2014 Triton 21TRX, 2017 Triton 21TRX and current 2022 Caymas CX21). I prop my boats for heavy tournament loads and the Fury just doesn't perform like the Tempest. On my new Caymas, the dealer installed a Bravo 1FS 25.5P. Great holeshot, midrange and bite but top end is not acceptable for me. I do send all my Tempest props to Mark Croxton so he can work his magic. Every setup differs, it all depends on what you want out of your boat and preference. I wish I could be more help.

  6. Member
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    #6
    Try finding a promax prop to try.

  7. Member lpugh's Avatar
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    #7
    Quote Originally Posted by Fishaholic Ty View Post
    raised the jackplate half an inch and lost 150 rmp and 2mph...lowered it back an 1/8th from where i started. I'm keeping my eyes out for a 4 bladed prop locally i can borrow.
    not possible
    Thank You Leon Pugh

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    #8
    Quote Originally Posted by Fishaholic Ty View Post
    raised the jackplate half an inch and lost 150 rmp and 2mph...lowered it back an 1/8th from where i started. I'm keeping my eyes out for a 4 bladed prop locally i can borrow.
    Interesting? Not the result I would have expected? If I raise my jack plate and it results in a mph loss, I have never seen the rpm drop. It usually increases or stays the same, meaning the slip increased. Running the jack plate lower on mine, will eventually result in an rpm loss and a mph loss due to the excessive drag.

  9. Member lpugh's Avatar
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    #9
    Quote Originally Posted by Pulsare2020 View Post
    Interesting? Not the result I would have expected? If I raise my jack plate and it results in a mph loss, I have never seen the rpm drop. It usually increases or stays the same, meaning the slip increased. Running the jack plate lower on mine, will eventually result in an rpm loss and a mph loss due to the excessive drag.
    That is a fact
    Thank You Leon Pugh

  10. Member
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    #10
    yea I don't know why it wasn't getting up to the rpms like before I raised it, I was at 5590 and after I was only getting to 5450. I don't think I had anything extra in the boat as far as weight, maybe a more full fuel tank. I lowered it once before with the old prop and lost about 50rpm and gained 1mph, due to bow lift i assume.

  11. Member 1BADAIR's Avatar
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    #11
    Were both props stock unworked? Not sure how rpm didn’t change between the two
    2011 Ranger z521/2023 250ProXS

  12. Member
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    Jul 2011
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    #12
    Do you remember what pitch tempest prop you ran on the 2017 21 trx? Also was it the 250 pro Xs 2stroke.

  13. Member
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    #13
    Quote Originally Posted by db_hud View Post
    Do you remember what pitch tempest prop you ran on the 2017 21 trx? Also was it the 250 pro Xs 2stroke.
    Yes, it was a 250 ProXS 2stroke. I ran the 25P in the cooler months and a 24P in the summer. If you run a fairly heavy load, the 24P would be your best option.

  14. Member Welaka's Avatar
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    #14
    Loss of bow lift due increased motor height. Lowering speed and rpm by same amount. Probably raise motor another 1/2 and lose more speed and rpm will start to go up with slip. I would guess PTP was pretty close
    2022 Caymas cx20pro 250 Pro XS s/n 3B099812

  15. Member lpugh's Avatar
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    #15
    Quote Originally Posted by Welaka View Post
    Loss of bow lift due increased motor height. Lowering speed and rpm by same amount. Probably raise motor another 1/2 and lose more speed and rpm will start to go up with slip. I would guess PTP was pretty close
    When the motor is raised to high, the prop slip increases due to surface air being pulled in, as a result the RPM always increases, bow drops as well as the speed
    Thank You Leon Pugh