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Ideal/Max RPM's on Mercruiser 351's Bertram 28 Moppie

Discussion in 'Bertram Yacht' started by KevinRinderle, Jul 11, 2009.

  1. KevinRinderle, Jul 11, 2009
    #1
    KevinRinderle

    KevinRinderle New Member

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    I have a bertram 28 Moppie w/ twin 351 Mercruisers. Is there such a thing as a max RPM that I should not push it above? Thus far I have taken them to 30 RPM's which gets me about 20-22 knots.

    Also has anyone experimented w/ alternate props or engine modification to make it go faster or more fuel efficient?

    Kevin
  2. Grecko, Jul 11, 2009
    #2
    Grecko

    Grecko New Member

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    Normal wide open throttle rpm's for the Mercruiser 351 (233 hp version) is 4200, so if you are only getting 3000 rpm, something is wrong. If the props are stock you likey aren't getting full power for any number of reasons from clogged air filters to some cylinders not hitting, to high drag in the drives, to something as simple as the throttles not opening all the way.

    First find out if you have the right props on it and check the throttle linkage, then go from there.
  3. NYCAP123, Jul 11, 2009
    #3
    NYCAP123

    NYCAP123 Senior Member

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    If I understand your question it sounds like you've only taken it up to 3,000 RPM's, not that it maxed out at 3,000. At 3,000 you should just be getting on plane. Your sweet spot should be at about 80-85% of max or about 35-3600 RPM's.
  4. KevinRinderle, Jul 15, 2009
    #4
    KevinRinderle

    KevinRinderle New Member

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    Correct. I have only taken it up to about 3000 RPMs. Being a newbie boater, and not having much history w/ the previous owner, I wanted to be extra cautious. 4000RPM's, here I come!
  5. NYCAP123, Jul 15, 2009
    #5
    NYCAP123

    NYCAP123 Senior Member

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    After the motors are up to temp max them just for a couple of minutes to see where that is; then cruise at about 80 % to 85% of max. That should be your sweet spot.
    Also, reproping can definately change performance as well as top and cruising RPM's, but on a mopie I'd guess the tweeking has already been done. You might consider having the props reconditioned though.