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  1. #1

    Default Cutting off the anti-ventalation plate ?

    I have 2 x Honda 40hp outboards on a 48' Catamaran. Top speed is 12kn. I want to fit large diameter props to increase power not speed. The existing props don't get enough grip/power in the water to manoeuvre the boat at less than 3kn in the marina when there is a breeze.

    A air of diesel motors can spin a cat and reverse the direction with the engines just ticking over I have to give the outboards a big rev then wait for the effect. Not good enough in a breeze.

    I have 4 blade props, max size. The anti-ventilation pate is the limiting restriction, can I cut it and fabricate one higher.
    Last edited by Dave_; 06-02-2020 at 12:50 AM.

  2. #2
    Join Date
    Sep 2010
    Posts
    19,546

    Default Re: Cutting off the anti-ventalation plate ?

    Welding may distort / bend the housings.-----Look into extension kits to lower the props.

  3. #3

    Default Re: Cutting off the anti-ventalation plate ?

    I didn't know there was such a thing. Thanks, I'll do that. Or did you mean make one ?

  4. #4
    Join Date
    Sep 2010
    Posts
    19,546

    Default Re: Cutting off the anti-ventalation plate ?

    A company called ----bay manufacturing -------They offer kits.----I do not know if they offer one for your motor.----Easy to look up I think.----Or contact a Honda dealer as they may have something.
    Last edited by racerone; 06-02-2020 at 08:41 AM.

  5. #5

    Default Re: Cutting off the anti-ventalation plate ?

    Have you looked into the possibility of lowering the motors down from where they are mounted now?

  6. #6

    Default Re: Cutting off the anti-ventalation plate ?

    Quote Originally Posted by Alan Hicks View Post
    Have you looked into the possibility of lowering the motors down from where they are mounted now?
    The pops are deep enough they don't move enough water to give me the control I need.

  7. #7

    Default Re: Cutting off the anti-ventalation plate ?

    I guess I was thinking that the deeper they were in the water, the denser the water becomes, which would provide more bite. Maybe not enough to be significant, don't know, but a lot cheaper to try than lowering the prop with an extension kit.

    I doubt seriously they're ever going to compete with a diesel rig though.....

    What size props are you running? Are they designed for commercial boats or maybe a pontoon boat? I know some of the crab boats that are using the 40's and 50's are using props WAY bigger than I've ever seen.

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