Long vs x-long shaft

Discussion in 'Outboards' started by voodoo92, Feb 26, 2015.

  1. voodoo92
    Joined: May 2014
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    voodoo92 Junior Member

    Hey there I know this is a question that has probably been asked a few times already but my phone isn't letting me search the forum properly for previous threads.
    Basically I'm designing a new build and aside from the obvious leg lengths and a small weight increase in the xl, is there any key advantages or disadvantages to either the long shaft vs the x long shaft outboards?
    If it matters I'm to be using the newer model mercury 150 four stroke.
    Thanks for your input
     
  2. whitepointer23

    whitepointer23 Previous Member

    X long puts an extra 5 inchs between the bottom of the power head and the water which is good on cats or mono's that sit low at the transom. But it also raises the engines cog as well and the fourstroke is quite heavy.
     
  3. voodoo92
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    voodoo92 Junior Member

    What would raising the engines cog ( I. Presume your talking about the centre of gravity) affect. Possibly make the boat roll a little more? And I was thinking of a suzi 140 but couldn't get any replies from Suzuki where as I received a reply from mercury within 12 hrs
     
  4. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    As WP23 says, it is sometimes advantageous to get the powerhead higher, in other instances only raises the overall COG of your boat, which doesn't help you any. I think you will find most boats today using that size of engine, especially offshore boats rather than say, ski boats, are taking the 25" option as standard. And many people re-motoring old boats, are raising the transoms to accept 25" motors.
     
  5. voodoo92
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    voodoo92 Junior Member

    Sorry to be annoying but what could some of the advantages be actually? I've started drawing a preliminary profile and hb view and will almost certainly redraw another one with that transom at 25" and doubt ill stop there haha
     
  6. SukiSolo
    Joined: Dec 2012
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    SukiSolo Senior Member

    Apart from the CoG and depth of prop etc mentioned above, there is also the issue of steering. The long shaft motors generally sit higher to allow rod/cable steering to be attached fairly easily. It is important to consider the run of this pretty stiff cable. The smoother and sweeter, the longer the inner will last and there will be smoother and more responsive steering.

    Some of the short shaft motors of old (much smaller Hp normally) were steered using a wire cable system usually nicknamed a 'washing line' system and this does not need the same motor height generally as the cable/rod system. Check the 'sweep' of the cable system as it exits from the rod mechanism just in front of the motor.

    In fact after dealing with several problems (too many) with cable runs - steering, throttle and gear change in recent production boats, I would advise getting hold of all the cables (maybe old broken ones?)and mocking up the entire run if possible.
    My experience is mainly on RIBs', Dories (Boston Whaler type) and a few others. Up to around 120 Hp.
    Time spent sorting a smooth cable run will repay later in compnent life and better boat handling. Very easy to get cable runs requiring new steering box and cable, each year or throttle and gearchange ones too....;)

    If your using hydraulic steering, all the comments about cable/rod steering above can be ignored. Still worth checking the throttle and gear cable runs though.
     
  7. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Check the product lines of the major engine makers, you may find that (sometimes) the 25" engines have a different gear ratio to the 20" version of the same engine. If your boat is designed for offshore use, I would opt for 25" transom height, if it is more designed for smooth water, with the emphasis on speed, 20" may be more appropriate.
     
  8. voodoo92
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    voodoo92 Junior Member

    Hydraulic steering will probably be the way to go for me but that's all really good info to remember. And out of the two choices there I'd say speed would probably take precedence over offshore use.
     

  9. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    The trend is definitely away from 20" transom height in larger outboards, in the future there may be a limited choice. 30" is even available in big outboards today.
     
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