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Controllable Pitch Props for Range Increase?

Discussion in 'Chris Craft Roamer Yacht' started by MikeB_2012, Nov 9, 2011.

  1. MikeB_2012, Nov 9, 2011
    #1
    MikeB_2012

    MikeB_2012 New Member

    Joined:
    Sep 7, 2011
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    2
    Location:
    Ontario, Canada
    Hi there. Has anyone put CPP on a Roamer to increase range? The two obvious benefits:

    a) both engines running more efficiently at all speeds;
    b) feather one prop and run on one engine efficiently for long range at slow speed.

    Anyone know if such a mod is possible, how much it might cost, and if it would be worth it? The reason I ask is that I might get a good price on a 55 foot Roamer (orig 8v71 I think, don't have all info yet) that I 'd like to fix up and do the Great Loop in and maybe Bahamas. I have heard however that any boat doing that kind of cruising should have a range of 400-500 miles and the boat's fuel capacity (400 gal) suggests that might be a stretch/impossible.
  2. Marmot, Nov 9, 2011
    #2
    Marmot

    Marmot Senior Member

    Joined:
    May 20, 2007
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    9114 S. Central Ave
    You would be better off just carrying a couple of 5 gallon fuel cans.

    A CPP wheel is expensive, it is less efficient than a fixed pitch propeller because of the larger hub, and unless it is installed with a properly programmed "combinator" the odds are very good you will suffer reduced time between engine failures related to overloading.

    CPP wheels sound good but they are not a "magic bullet."
  3. Capt J, Nov 9, 2011
    #3
    Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
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    14,529
    Location:
    Fort Lauderdale
    8v71's are extremely fuel efficient if you keep them under 1000 rpms, and if you keep them at 800 rpms, they're twice as fuel efficient as 1000rpms. You can run them at those speeds for 4-6 hours, then run them at cruise to clean them out for 30 mins. You'll probably burn 8gph for both at 1000rpms, and around 5gph for both at 800 rpms, and most of the great loop you're going to have to do hull speed anyways. I did the great loop in a 75' Hatteras with 12v71 TI's and ran at cruise a couple of days and still averaged 1.5 GPM including generators and we stayed on generator overnight 75% of the time......I don't think you'll see a big enough gain with variable pitch propellors.