I'm in the market for an outboard

Discussion in 'Outboards' started by Commuter Boats, Oct 3, 2016.

  1. Commuter Boats
    Joined: Oct 2006
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    Commuter Boats Commuter Boats

    There's a reason that they're starting to produce some outboards with 35 inch shafts, on many of today's big outboard boats, a 20 inch shaft would have the power head in the water so the only way to talk about shaft length is to talk about it in relationship to a particular design.

    I'm sorry that the conversation got sidetracked and focused on a 20 inch shaft, the necessity of that length was determined very early in the design process and only comes into this conversation as it limits my options.

    I have requested the paperwork from my dealer to be presented to my bank so at this time I have plotted a course and I appreciate all the help I've received to get that done.
    Gerald
     
  2. CatrigCat
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    CatrigCat Junior Member

    How fast will the boat go?

    The gearing on the Honda would suit a faster boat while the numerically higher gearing of the Suzuki would make for a more efficient propeller at slower speeds.

    As for charging batteries, outboards dont run long enough to charge anything.
     
  3. Commuter Boats
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    Commuter Boats Commuter Boats

    The boat should be able to achieve 45 kn and although the average outboard in the United States is operated in the neighborhood of 50 hours per year, that does not represent the expected service that this boat will see. The boats operational area is Southeast Alaska and it will have a 300+ amp hour house battery bank, furnace, inverter, electric potholder etc.

    The Honda claims 48 Amp at one thousand rpm which can substantially reduce the impact of a 80 amp draw while pulling shrimp pots out of 60 fathoms.

    I'm certain that that I will make good use of the 60 Amps that's available from the Honda and the vessel will carry a portable generator for the times when that's inadequate.


    Gerald
     
  4. gonzo
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    gonzo Senior Member

    I think that the cut-out on the transom is the lowest point where boats of this type tend to flood from. Since that is already set, then the leg length is also set; I agree.
     
  5. TANSL
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    TANSL Senior Member

    I do not know exactly what type of boat you mean but, overall, the downflooding point is usually not the "cut-out on the transom". It can be, no doubt, but does not have to be.
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    Good point about the gear ratio, it is not a high speed boat and if there was a bigger reduction available in a 20", would probably suit.
     
  7. Commuter Boats
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    Commuter Boats Commuter Boats

    The gear ratio on most of the large Suzuki's is 2.29:1 their 20 inch shaft length 250 horse ( model DF 250 SS ) utilizes the same lower unit as their 300 horse does and that provides a 2.08:1 reduction. Hondas 200 and 225 horse utilizes a 1.86:1 but for the 250 they offer 2.00:1 so the differences aren't huge. I do believe the Suzuki can swing a slightly larger diameter propeller ( I think .25 inches) and of course that would be desirable but I haven't been particularly happy with the large diameter propellers that are available for Suzuki's and there's pretty good offering of four blade propellers for outboards today which helps quite a lot to compensate for diameter.
    I appreciate the continuing points.
    Gerald
     
  8. Commuter Boats
    Joined: Oct 2006
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    Commuter Boats Commuter Boats

    There's a few people following this thread so I thought I would throughout a few photos,
    The hull that I'm working on now just out of the mold and without a 4 foot extension.
    Two pictures of its sister, not lengthened but with a 25 inch outbourd.

    The project I'm on now is of similar weight ( hopefully a little lighter ) but with quite a lot more buoyancy. The planing surface has been extended by 2 feet and a full beam, 2 foot long molded bracket has been fabricated.

    As you move the outboard aft away from the transom we will typically raise the outboard 1 inch per foot of setback so with my 2 foot setback as compared to a 1 foot setback on her sister, the anti-ventilation plate would be 1 inch higher. So with the 5 inch shorter shaft and the 1 inch higher mounting, the power head would be 4 inches lower. Due to the increased buoyancy the water line should be 2 inches lower so I'm really not concerned about my mounting height.
     

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  9. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    The photo explains a lot. I was visualizing a typical transom cut-off. You have a considerable adjustment on the plate also, which makes the leg length less critical. Nice boat.
     

  10. Commuter Boats
    Joined: Oct 2006
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    Commuter Boats Commuter Boats

    Thank you, please keep in mind that that's a sister, I built that one for a client and launch it in 07, the project I'm on now is for my lady and I and it's about a month away from the water. The stern is very different but the relationship between the mounting surface for the engine and the freeboard of the vessel is similar.
    Gerald
     
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