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Thread: Yanmar 100 hp

  1. #1

    Default Yanmar 100 hp

    24 feet boat with 2 Yanmar 100 hp with turbo. I would like to check what is wrong as the boat only gives 10 knots. And how much RPM should 2 100hp give?

  2. #2
    Join Date
    May 2015

    Default Re: Yanmar 100 hp

    Knowing the engine model, the hull and the rpm you run at would help. You're probably up against hull speed. H = 1.34 √(L)
    H (speed in knots) = 1.34x square root of the boat length. In your case about 6.5 knots. Unless you can plane, it takes a lot of hp to go above your hull speed. If you ran at 6 knots, your fuel bill would be about half.
    If you want to go faster and you have a planing hull, then twin 2-300 hp engines should do. If you have a displacement hull, you won't get much more speed. Or get a longer hull. I have an 83' boat with 2 - 200hp engines and can do about 12 knots. Hull speed is 12.2.

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