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  1. #11
    Join Date
    Feb 2015
    Location
    Conwy
    Posts
    2,008

    Default Re: What hp longshaft back up auxiliary outboard for a 23ft 2.5 tonne planing hull mo

    Quote Originally Posted by TheOrs View Post
    Mine is a four stroke (if it was me you were asking). Yamaha F6CMHL with the lowest pitch propellor available.

    I've not used it in bad weather or an emergency but it seems to cope quite well against a moderate tide.
    Then 6hp re weight wise is about as big as you can realistically go

  2. #12
    Join Date
    Aug 2002
    Location
    Stratford upon Avon & S.Devon
    Posts
    5,164

    Default Re: What hp longshaft back up auxiliary outboard for a 23ft 2.5 tonne planing hull mo

    Quote Originally Posted by BruceK View Post
    Then 6hp re weight wise is about as big as you can realistically go
    Think you will find that with some brands their 8hp models weigh the same as their 6. Or at least that used to be the case.

  3. #13
    Join Date
    Feb 2015
    Location
    Conwy
    Posts
    2,008

    Default Re: What hp longshaft back up auxiliary outboard for a 23ft 2.5 tonne planing hull mo

    We're splitting hairs here. The OP wanted a recommendation on hp for an auxiliary motor. The obvious answer is : as much hp as weight will allow to cover the most conditions he might experience. That is a ~10hp 2 stroke. Sure he can go less. I imagine even a 1hp will push his boat in the most absolute ideal conditions. Not fast granted, but it will push it, eventually.

  4. #14
    Join Date
    May 2001
    Location
    South coast
    Posts
    3,067

    Default Re: What hp longshaft back up auxiliary outboard for a 23ft 2.5 tonne planing hull mo

    I'm not sure it's quite that cut and dried. Since the auxiliary engine is not going to plane the boat, arguably the smallest engine that will push it at displacement speeds (5 knots for a 23ft boat?) against a bit of headwind is perfectly sufficient. Bear in mind that auxiliary brackets are not always the strongest, so the torque of an overly powerful engine for the job trying to push the boat faster than it will go could cause issues.

    Also a smaller more economical engine is going to achieve more range for a given (and probably limited, unless the OP has a way of tapping into the boat's main tank) fuel supply. Add in the weight saving of a smaller motor making it easier to deploy if not permanently fitted (and reducing bracket load if it is - bearing in mind small planing boats tend to bounce around).

    I'd have thought that for a Falcon 23, a 6hp engine ideally centrally mounted on the transom rather than offset, would be sensible.
    Ari

    ---------------------------------

    If a man speaks in a forest, and there is no woman to hear him, is he still wrong..?

  5. #15
    Join Date
    Feb 2015
    Location
    Conwy
    Posts
    2,008

    Default Re: What hp longshaft back up auxiliary outboard for a 23ft 2.5 tonne planing hull mo

    Quote Originally Posted by ari View Post
    I'm not sure it's quite that cut and dried. Since the auxiliary engine is not going to plane the boat, arguably the smallest engine that will push it at displacement speeds (5 knots for a 23ft boat?) against a bit of headwind is perfectly sufficient. Bear in mind that auxiliary brackets are not always the strongest, so the torque of an overly powerful engine for the job trying to push the boat faster than it will go could cause issues.

    Also a smaller more economical engine is going to achieve more range for a given (and probably limited, unless the OP has a way of tapping into the boat's main tank) fuel supply. Add in the weight saving of a smaller motor making it easier to deploy if not permanently fitted (and reducing bracket load if it is - bearing in mind small planing boats tend to bounce around).

    I'd have thought that for a Falcon 23, a 6hp engine ideally centrally mounted on the transom rather than offset, would be sensible.
    Agreed to a point. A 6hp 4 stroke is going to weigh the same if not more that a 10hp 2 stroke, so why given the choice would you go less?
    You also want some manoeuvrability and for that you need a bit of torque, the presumption here that you are going to get that with a bigger hp / cm3 engine.
    You also dont want to be using all the hp all the time straining the motor. Going to max hp to start momentum then throttling off .
    Your argument that the smallest motor possible would be very limiting imo. Here is a vid taken many moons ago of me pushing a 1 ton boat against a headwind and mild current only being able to make 2knts and this is with a 8hp motor that's such a wonderchild I still have it. Would it push a 2.5 ton Falcon which has much more windage in the same conditions, I think there is room for more than a little doubt.


  6. #16
    Join Date
    Mar 2004
    Location
    Bristol UK
    Posts
    1,077

    Default Re: What hp longshaft back up auxiliary outboard for a 23ft 2.5 tonne planing hull mo

    9.9 hi-thrust would be as good as anything else
    Needs to be a big foot/sailpower/high-thrust model not a standard engine. Will work as an engine for the tender but won't be ideal.
    Why can't we work 2 days a week and boat the other 5????

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