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Props for a Navigator 53

Discussion in 'Technical Discussion' started by Audacious, Jul 28, 2017.

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  1. Audacious, Jul 28, 2017
    #1
    Audacious

    Audacious New Member

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    Just buying a 1998 Navigator 53 Classic Pilothouse. Props are 32x32x2. I have a suspicion that the props are oversized. Engines are TAMD63Ps 370 hp. Displacement is 43,000#. Boatdiesel's prop calculator comes up with something like 27x24. Today, I noticed that the last Navigator product descriptions (5200 at 50,000# and Yanmars) showed a spec of 28x28. Can anyone share any info? Also, if I change prop sizes, what else might need to be changed?
  2. PacBlue, Jul 29, 2017
    #2
    PacBlue

    PacBlue Senior Member

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    What is your maximum rpm at wide open throttle? This should be done with a clean bottom, full fuel and water, no waste.
    It is not unusual to reduce pitch over time as your boat gains weight/gear.
  3. Capt Ralph, Jul 29, 2017
    #3
    Capt Ralph

    Capt Ralph Senior Member

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    That prop calculator is wrong for my boat also, even though my wheels are to factory spec and all similar boats (to mine) are swinging the same size (32x32x2.5).
    I've tried it for other boats on the hill for ship and giggles, it was wrong for them also.

    Are you having performance issues? Is there a factory spec in your manuals?
  4. Audacious, Jul 31, 2017
    #4
    Audacious

    Audacious New Member

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    On a sea trial two weeks ago top was 2600.
  5. PacBlue, Jul 31, 2017
    #5
    PacBlue

    PacBlue Senior Member

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    So the rpm you are looking for is 2800 - 2850.

    If the bottom was clean, the engines are in a good state of tune (developing full power) you will most likely need to reduce some pitch. I also like to take rpm measurements in 2 directions to account for any current/wind. Also, you should check the No Load (Neutral) rpm at the dock to make sure you have full throttle travel available at the controls.

    1" Reduction in pitch will get you about 200 rpm's. Your prop shop should scan and get the correct pitch measurement first, and then bring them back to a true Class S Tolerance level complete with scans. For your reading: http://www.wildcatprops.com/articles-iso484-standard.asp

    If you are going to do this at a haul out, good time to replace the struts cutlass bearings and re-align everything as well.