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Difference in long/short shaft outboards

  • 04-01-2008 8:35pm
    #1
    JasonEFlood
    Closed Accounts Posts: 16 ✭


    I'm buying a brand new 15hp outboard for the back of my punt - had a question maybe some of you can help me with. As I am buying it new - I have full choice - and was wondering - whats the difference between short and long shaft.


    I understand one sits shallower in the water (for weed avoidance etc) - but from and engine performance point of view - does the short shafts at high revs/speeds come out of the water, as the boat starts to plain?

    Also the boat will be used in the sea - so there will be waves, would you advise going longshaft, as probably be bouncing in the waves etc - would it be better for the long shaft as less likly for engine to exit crossing the troughs of the waves?


Comments

  • #2
    Alkers
    Registered Users, Registered Users 2 Posts: 6,908 ✭✭✭Alkers


    Ask the dealer but I'd imagine the short shaft version is what you're after. I think long-shaft are used for attaching to the back of yachts or larger boats while short shafts are for speedboats or dinghys.


  • #3
    JamesM
    Registered Users, Registered Users 2 Posts: 1,775 ✭✭✭JamesM


    JasonEFlood wrote: »
    I'm buying a brand new 15hp outboard for the back of my punt - had a question maybe some of you can help me with. As I am buying it new - I have full choice - and was wondering - whats the difference between short and long shaft.


    I understand one sits shallower in the water (for weed avoidance etc) - but from and engine performance point of view - does the short shafts at high revs/speeds come out of the water, as the boat starts to plain?

    Also the boat will be used in the sea - so there will be waves, would you advise going longshaft, as probably be bouncing in the waves etc - would it be better for the long shaft as less likly for engine to exit crossing the troughs of the waves?

    It depends on the depth of your transom - a small inflatable would have a short shaft, while your punt might need a long shaft. You have to do the measurement and see which will have the prop deep enough in the water. Sometimes even with a long shaft, you might need a cut-out on the top of the transom, which will lower the engine.
    Jim.


  • #4
    250882
    Closed Accounts Posts: 206 ✭✭250882


    I remember reading on another website that the lowest part of your keel at the back of your boat should be level with the fixing plate just above the gearbox of the engine. Thats how it is on my boat but please get some conformation its third hand advice now.


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