Re-powering a houseboat - Stay with Stern drive?

Discussion in 'Propulsion' started by paticus, Oct 10, 2023.

  1. paticus
    Joined: Sep 2023
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    Location: Norther California

    paticus Junior Member

    I have a 50ft houseboat (~50k lbs), that currently has a dead 3.0 mercruiser with an Alpha One Stern Drive.

    I am pulling the boat this Winter to get new Aluminum pontoons and engine pod. I was planning to replace the engine/outdrive as well. These Sterndrives seem great on boats that get trailered and can be pulled easily for maintenance, but not for a houseboat that sits in the water for years at a time.

    My question...
    Since I am getting a new engine pod built, should I consider transitioning to an Inboard?

    BTW I'm not interested in an outboard (although they sound great), due to a rear deck/swim platform that I want to keep unobstructed.
     
  2. kapnD
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    kapnD Senior Member

    You will have handling problems with an inboard motor, unless you choose dual motors, one in each pontoon.
    Stern drives have a huge advantage there, as their direction of thrust is articulated.
     
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  3. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    What is the beam of your houseboat?
    If you had a pair of outboards, one on each hull transom, then you would be much more manoeuverable, and the mid section of your aft deck would still be relatively unobstructed?
     
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  4. paticus
    Joined: Sep 2023
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    paticus Junior Member

    20ft, good point.
     
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  5. DogCavalry
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    DogCavalry Senior Member

    And you wouldn't have to build a pod, which absolutely is terrible for performance.
     
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  6. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell . . . _ _ _ . . . _ _ _

    Would hanging an o/b off each new pontoon (designed for them) leave the swim-grid clear enough?
    This would be a great set-up, build your fuel systems, etcetera into the pontoons.
    A 20' beam on a 50' hull is a maneuverability challenge, no?
    Directable thrust on widely spaced twins would serve you well.
     
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  7. BlueBell
    Joined: May 2017
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    BlueBell . . . _ _ _ . . . _ _ _

    This is not a houseboat it's a floathome or floathouse.
    Did I miss something, how fast do you expect this to move under power?
    How much power did you have in mind, or was that your next thread?
     
  8. kapnD
    Joined: Jan 2003
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    kapnD Senior Member

    OP calls it a “houseboat”.
    What’s the difference?
    Does it have any bearing on how the craft is powered?
    Maybe the OP should state travel range and speed requirements.
     
  9. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    A 3.0 Mercruiser has 140 HP. The cheapest option would be a pair of 70 HP outboards. Pods add a lot of drag and not a lot of benefits. If the boat stays in the water for years and only moves occassionally, a jack plate will make it possible to raise the outboard completely out of the water.
     
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  10. DogCavalry
    Joined: Sep 2019
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    DogCavalry Senior Member

    The 3.0 used car reporting horsepower. It has 140 at the crankshaft. It delivered 100 hp at the prop, so the power demands are even less than that. But definitely need the performance numbers for the boat. In a boat like that the speed/drag curve is extremely non linear, and 25hp might move it almost as fast as 100.
     
  11. gonzo
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    gonzo Senior Member

    There is no way it loses 40HP from the gears. Maybe 5 to 7. Further, claiming that 25 HP will move the boat at the same speed as the 3.0 makes no sense.
     
  12. BlueBell
    Joined: May 2017
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    BlueBell . . . _ _ _ . . . _ _ _

    OP seems to have lost interest despite several Forum visits, so it's all a mute point.

    Well, accept for the three pages of arguing that's about to ensue over nomenclature and HP.

    BB
     
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  13. gonzo
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    gonzo Senior Member

    We can wrap up the argument in 2 1/2 pages.
     
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  14. kapnD
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    kapnD Senior Member

    “What we have here is a failure to communicate “
    I see here a willingness to discuss this subject, but a lack of details and input from the OP making meaningful discussion impossible.
     
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  15. DogCavalry
    Joined: Sep 2019
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    DogCavalry Senior Member

    Yes, it does. And I'm starting to think you need remedial reading courses. You can't tell when I'm quoting someone else, and you can't tell the difference between close to and the same. The output at the prop is from their own documentation, and that includes all peripherals. Cooling losses, electrical generation, and the complex gearing path(1). Maybe learn a little about engines, while you're brushing up on your reading skills?

    1- Ogorkiewicz, R.M. Janes Technology of Tanks
    1991, 227
     
    Last edited: Oct 14, 2023
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