Cygnus 19' GRP displacement fishing boat in England - a question re the engine

Discussion in 'Powerboats' started by bajansailor, Oct 10, 2021.

  1. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Here is a link to a thread posted on the YBW Forum in England, by a chap who has a 19' Cygnus open fishing vessel in Exmouth, Devon.
    Small engine options

    The original post noted :
    "Thinking about changing the engine in my cygnus 19 open boat. Currently installed is a Volvo md17d (36 hp) which is a bit over powered and thirsty for the boat. Was re-engined by previous owner from an 18hp. Id like something as small as possible around the 16-20 hp range that would hopefully allow me to slightly raise the deck and make it flush with scuppers and remove the need for an engine box. Current engine has a 300mm high engine box."

    She seems to be an older version of this 19' Cygnus currently being built -
    Cygnus GM19 | Cygnus Marine Boats

    Here is a basic plan and side elevation.

    Cygnus GM 19 GA.jpg

    Herr owner Anthony notes (later in the thread) that on his boat the engine is actually further forward than shown above, ie it is between frames 3 and 4 from the bow.

    Rather than suggesting that he 'sign up' over here as well to post his question, I thought I would ask on his behalf, and ask him to have a look for your thoughts and suggestions - all are most welcome!
  2. Rumars
    Joined: Mar 2013
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    Location: Germany

    Rumars Senior Member

    The MD17 is 689mm tall (HD versions 740mm). The modern replacements are all around 5XXmm, so that shaves around 150mm, or half his engine box height. The other 150mm can probably be had with a combination of adjusting the propshaft angle, moving the engine further back and raising the floor, but it's a lot of work for not much gain.

    Modern diesel engine heights: Beta 16&20hp (Kubota) shallow pan 519mm, normal pan 560, Lombardini 18&27hp 522mm, Sole (Mitsubishi) 17hp 542mm.

    Another option would be to modify an engine to work in a horizontal position (oil, exhaust, cooling, etc.) wich is as much work as before, just of a different kind.

    If the use case fits (range, speed) he can go electric, that fits all under the existing floor.
    bajansailor likes this.
  3. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    I wonder what the problem is with the engine box protruding ? In any case, raising the floor won't help the stability. Sounds like it ships a little bit of water, a bilge pump would fix that.
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