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  1. #1

    Default 21" 3-blade to 23" 4-blade?

    Johnson 70hp VRO has now 13x21 Solas Amita 3 aluminum prop.
    Boat is Argo 17 race boat, this combination is capable to +/-50kn. (with cleaver etc.)
    Solas says that this prop has wide blade design ment especially for 4-stroke engines.
    Johnson revs 5600 wot and takes 39kn, with wife an kid in boat.

    Now, considering more top speed, I have an opportunity to buy a 13.25x23",OMC Renegade for reasonable good price. However 4th blade and 2" gain in pitch makes me wonder... Is it too much?
    I have a jack plate and there's fairly much to lift engine more. I think Renegade would work much better lifted than Amita.
    But how this "wide blade design" alu compares to 4-blade steel?
    Is it worth to try or do I see revs drop under 5000?
    Opinions are welcome.

  2. #2

    Default Re: 21" 3-blade to 23" 4-blade?

    Thanks.
    I'm aware that ~200rpm drop per inch, but what I'm not aware that how affects one more blade? Will it drop more or not? And my motors rpm range @wot is 5000-6000.

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