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Thread: 85 272ls. 54mph

  1. #1
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    85 272ls. 54mph

    Trimmed and as far as the throttle will go, can only go 54 at 3400rpm. Twin 350. 3 blade knifed props, not sure what the pitch is. Shouldn't I have more left to go?

  2. #2
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    What pitch are the props?

  3. #3
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    Either your tachs are both wrong or you are way over proped. That speed at 3400 sounds like 23" props....and at 3400 you are just getting into the peak of the torque curve. Check the last 2 digits on the part number...thats your pitch.

  4. #4
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    You're over-propped. Size the props to see upper 4k rpm's.

  5. #5
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    Besides speed. What harm am I currently doing to the boat if any?

  6. #6
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    Not really any serious harm in the short term...but you are for sure burdening the engines. Just for comparison...my 255 w/twin 350 Chevys, which is very close in size and weight as your 272 is turning 4300 RPM at 54 MPH and 5100 at 62~63.

    I'm running 19" pitch and should be running 21"....I am slightly under proped....I keep my RPM at a max of about 4700~4800 by backing off.

    Take a look at those props and let us know what you are running. If you are running Alphas with 1.5 gears your numbers should be close to mine.

  7. #7
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    Quicksilver 48 89804a5. 23p

  8. #8
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    Over proping bogs the engine making more heat and detonation. Long term......boom.
    You should see about 4,400 to 4,800 rpms on stock motors.

  9. #9
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    Quote Originally Posted by Fivepnt0 View Post
    Quicksilver 48 89804a5. 23p
    OK...(the math still works) your running a 23" pitch...way too much prop. I'll bet your 27 is a pig out of the hole...especially with a load.

    See if someone local can hook you up with a pair of 19" on loaner (even if they're aluminum) to see where that puts you.

    I'm guessing your optimum is going to be a Mirage Plus Stainless in a 19" pitch.

    What part of the country are you in? Check craigslist in your location and search under boats for "prop" in "title only".

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