Planning to build a small boat

Discussion in 'Boat Design' started by sigourneyanderson, Sep 22, 2021.

  1. sigourneyanderson
    Joined: Sep 2021
    Posts: 1
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    Location: Ukiah, CA, USA

    sigourneyanderson New Member

    Helle everyone,

    I am planning to build a small boat with an inboard engine. The engine comes from an old generator that I fixed a couple of days ago.

    The idea to build a boat is something I want to do for a long time now and now I have an engine I want to start building. The only problem I have right now is that I want some sort of gearbox to be able to put my boat at least in neutral or maybe even in reverse.

    Does anyone have a suggestion for a gearbox?

    Thanks in advance!
  2. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    The first thing to understand is that such an engine may be unsuitable, on grounds of fire risk and cooling problems in the confined space of a small boat, before worrying about gearboxes and what not.
    bajansailor likes this.
  3. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    +1 re Mr E's thoughts above.
    In addition, I think that you should find a boat that really appeals to you first of all, and then assess it as to how easy / viable it would be for you to build it.
    And to power it.
    There are so many small boat plans available for sale on the internet for not a lot of $$'s - and if you think the cost is a lot, then just stop, as you can't afford to build it.
  4. comfisherman
    Joined: Apr 2009
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    Location: Alaska

    comfisherman Senior Member

    Would be helpful if we knew the engine type?

    If it's a fairly standard small diesel engine it usually requires a different fuel pump as generator pumps are constant speed variable load and propulsion engines need variable speed. From there you would usually need to know bell housing and flywheel size. Best case scenario it's relatively standard albeit a bit of a long shot and you can find some kind of second hand gear that fits close enough that all you need is adapters. Then the issue of exhaust temp, if it's a common motor sometimes you get lucky and there are off the shelf marinization parts.

    In my case a friend smoked an Isuzu Gen end and it was faster to replace the whole unit than the end, year later we swapped it into a little launch for putting around. It was 700 for the fuel pump and maybe 350 for the bellohousing adapters to a gear we had laying around.
  5. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    We need more info on the engine. As Mr E said it may not be suitable for an inboard installation. If it's a gasoline engine it may require too many changes to make it suitable for marine use. The cost would be better spent on a small outboard. If it's a diesel, as Comfisher pointed out, there are also changes that need to be made. Generator engines are designed to run at constant speed under relatively light loads, whereas marine engines run at a range of speeds and under heavy load.

  6. rocco611
    Joined: Jan 2019
    Posts: 60
    Likes: 16, Points: 8
    Location: Madera Ca

    rocco611 Junior Member

    The engine you have might better suited as mud motor than an inboard. there are lots of kits out there to build mud motors or convert it to run a fan and build an air boat. :)
    DogCavalry likes this.
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