Wellcraft Diesel Conversion

Discussion in 'Boat Design' started by studlybilly, Sep 12, 2007.

  1. studlybilly
    Joined: Sep 2007
    Posts: 1
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Jackassville, Florida

    studlybilly New Member

    Hello and sorry if this is in the wrong forum, I can't really seem to find any technical boat forums to ask my question.

    I have acquired a 1985 26' Wellcraft Aft Cabin, which currently has a mercruiser 350 in it. I have 2 Cummins 4bt (4 cyl, 3.9L) diesels lying around, and I'm hoping I can convert one of them in the Mercs place. We will be fueling the engine to 250hp @ 2500 RPMs. I just have a couple questions.

    1. My sterndrive is a Merc Bravo I (IIRC) with a 1.47:1 ratio, given the diesel wont be turning the rpms that the V8 does, I'm thinking this will turn the boat into a slug. Does anyone know what alternatives there are to this? Optimum would obviously be more of an overdrive ratio of .5-.8:1 to keep the prop speed up.

    2. The Merc engine weight as I seen through specs online, is 1200lbs, the 4bt fully oiled up etc. is 800lbs. So there should be no concerns with the hull holding up?
     
    studlybilly, Sep 12, 2007
    #1
  2. skiffish
    Joined: Jul 2005
    Posts: 17
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: ca

    skiffish Junior Member

    4bt

    I am not sure of options for spinning prop faster with that drive other than using a larger prop or diff pitch for some more push.

    I would be interested if you are selling the extra 4bt. I would be putting it into a direct drive and i know the options to gear up or down are good in that aplication.
     
    skiffish, Oct 17, 2007
    #2
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