Pros & Cons of 1 engine/sterndrive VS 2 engine/sterndrive setup on 43' Houseboat?

Discussion in 'Propulsion' started by Wado, Jan 19, 2011.

  1. Wado
    Joined: Jan 2011
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    Location: Maine, USA

    Wado Junior Member

    I want to repower my 43' 1983 Gibson Houseboat with one 230 to 260 hp diesel/sterndrive package. The original power was provided by 2 Volvo Penta 260 hp gasoline engines with 280 Outdrives.
    I don't need the boat to go fast but would like to be able to cruise in the 8 to 10 knot range.

    This fiberglass boat weighs approximately 20,000 pounds and has a V shaped bow with a very flat hull.

    A dealer for Steyr Diesel motors told me that after consulting with his team he could not recommend replacing the two motors with a single because it would compromise the handling too much especially when dealing with wind and current in a docking situation.

    Will the addition of a bow thruster to the single engine propulsion give me sufficient control ? He was reluctant to accept that as a solution.

    As much as I would love to replace both engines with 2 diesels the cost is prohibitive for my budget. I will be doing the fiberglass and engine bed work myself so the cost of the labor to make this switch is not a factor.

    Can I get some help from the members on this question?
    Thanks,
    Wado
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    A sterndrive and bow thruster combination can give you adequate maneuverability. That is a rather heavy boat, and I assume has a lot of windage too. It is hard to make a speed prediction without that data. In a blow, 260 HP may be marginal.
     
  3. Wado
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    Wado Junior Member

    Picture of boat attached

    Gonzo,
    Thanks for the input on handling. I've attached a picture of the boat so you can get an idea of the surface area for speed calculations.
    The height from the deck to the roof is 6' 3".
    Wado
     

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  4. gonzo
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    gonzo Senior Member

    I think you will have a hard time getting a bow thruster to work. The bow is quite flat and shallow. What is the problem with the existing outdrives. If they are serviceable, you can just replace the engines.
     
  5. Wado
    Joined: Jan 2011
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    Location: Maine, USA

    Wado Junior Member

    Bow thruster is external

    Gonzo,
    I am going to use an Exturn Thruster which mounts externally.

    I want to switch to diesel for safety and fuel economy.
    My wife and I plan to live aboard and travel.
    The original engines and sterndrives would need a complete rebuild. They are carburated and are raw water cooled. I want fresh water cooling and fuel injection.
    I have completely rebuilt the boat and really want a new or factory reman diesel. I'm just hoping I don't have to buy 2 to get a decent level of performance and handling.

    Wade
     

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  6. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    A single I/O and thruster will work, but you've dramatically reduced your HP output with a single drive installation. In other words, going from 520 HP down to 230 is a 66% reduction in available output. That's well beyond a huge reduction. Yes, you'll do 10 MPH, but your fuel use will be quite poor. Making substantial changes to drive configuration, CG concerns and other issues, just begs the question of, why haven't you contacted a NA, designer or marine engineer yet? You just can't make this level of "upgrades" without consideration of the "ramifications" that these decisions will impart on the yacht as a whole. For example, the Marrino unit is an interesting choice, though it will increase the draft of your boat considerably. Or, removing 5% of the vessel's displacement from the stern will surly move the CG forward a fair bit. You do realize this isn't a passage maker, nor a trawler, but an over powered house boat, right?
     

  7. Wado
    Joined: Jan 2011
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    Location: Maine, USA

    Wado Junior Member

    The more you learn, the more you realize you don't know.

    Par,
    Thank you for your insight. I do realize that this is a houseboat and I realize that my cruising will be coastal and limited to good weather.
    I have not contacted a Nautical Engineer because I did not think that this change would radically affect the boats handling. I grew up lobstering with my dad and we had a 32' Jonesport with a Detroit Diesel. I know that the hull is significantly different but my gut instinct was that a single I/O would work fine.
    I look forward to more discussion on the subject so I can decide how to proceed.
    Wado
     
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