Why inboard shaft drive is popular in ski boats but not in smaller CC sportfishers

Discussion in 'Powerboats' started by Northeaster, Aug 27, 2012.

  1. powerabout
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    powerabout Senior Member

    an outboard will actually hold the speed better at the top end of the tournament scale especially noted in jumping where the skier pulls longer
    Small pitch huge revs 15" diameter prop bigger than an inboard but at 2:1 gear ratio at peak torque you wont pull it back as much as an inboard that is well past peak torque
    Jump world records only moved forward once they started using outboards in the late 80's
    saying that I would never go re recreational skiing with an outboard
     
    Last edited: Dec 18, 2012
  2. Frosty

    Frosty Previous Member

    Absolute rubbish.
     
  3. powerabout
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    powerabout Senior Member

    ok I did go skiing once with an outboard
    do the math, torque curve peak outboard versus inboard and at slalom/jump speed you will see the 4 stroke is in over its head.
    Of course this only applies to 2 stroke outboards hence they have dropped off in popularity, not the mention US builders make way more money with an inboard boat sale versus and outboard and multi use boats are the bigger seller now rather than barefoot/tourny boats
     
    Last edited: Dec 18, 2012
  4. powerabout
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    powerabout Senior Member

    Baeckmo
    I cant see where you could possibly think a higher ratio like 1:1 can possibly out accelerate a lower ratio
     
  5. michael pierzga
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    michael pierzga Senior Member

    At the shipyard this week is a CC that slipped off it trailer and punched a hole in the bottom.

    Since its an outboard powered boat the composites gang unbolted the outboard, drained the gas tank , prepared the hull, then flipped the hull upside down with a forklift so that they could easily repair the damage.

    This would be too expensive with an inboard powered boat.
     
  6. IMP-ish
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    IMP-ish powerboater

    A shop with a proper overhead hoist and tools will hoist out an inboard in an hour and have it in again in a few hours. Not that big a deal compared with the fiberglass repair.
     
  7. powerabout
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    powerabout Senior Member

    you forgot about all the seized rusted mounting bolts and coupling bolts
    New yes I agree, after a few years in salt, the outboard will be faster with less lifting gear, less to go wrong, easier to quote on.
     
  8. powerabout
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    powerabout Senior Member

    Plenty of outboards have passed the AWSA certification which includes all those tests, clearly now that the outboards are 4 stokes that torque that the 2 strokes had at higher rpm is gone.
    Whilst we are talking US boats, the ski boat manufactures have no incentive to sell outboards at all, that makes the big picture look a bit skewed. Probably game over now that heavy slow boats for wake boarding is probably the dominate market.

    And yes a badly designed inboard is a better ski boat than a badly designed outboard one.
     
  9. michael pierzga
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    michael pierzga Senior Member

    Well, if it were and inboard you propably would have had to haul the engine and complete drive line because to damage was aft near an inboards engine room .

    I like inboards. Its important to have the correct design and size. For years I used to go fishing on a Carolina Style cc. 23 footer with its diesel installed under the CC. It was a nice boat, not fast..perhaps 20 knots...weight centered, not hung off the stern,,so it could bash to windward at reduced throttle and still ride on its lines.
     
  10. 805gregg
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    805gregg Junior Member

    I timed myself getting my 383 chevy ready to remove, it was 45 min and done, not too expensive.
     
  11. 805gregg
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    805gregg Junior Member

    If you are in Canada, a CC would be a bad boat choice, too litle wind protection and it would be wet and cold.
     

  12. Yellowjacket
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    Yellowjacket Senior Member

    There are numerous reasons

    There are a number of reasons most have been mentioned above, but taken in totality the layout has endured because it was, at the time, superior to the basic outboards that were available. The water ski enthusiasts want to use a boat similar to that used in competition, if for no other reason that they think that’s the best boat for the job.

    When competition skiing was getting started, inboards were far superior to outboards in the ability to tow a skier at a constant speed with a low wake. Virtually all of the competition boats were inboards (Correct Craft and Master Craft) and the people who were practicing for competition want to practice with the boats they would use in competition. The fundamental superiority of the layout has kept it going all this time. Boats used for competition have to be certified by the US Waterski Association and right now only inboards are approved, although I don’t know if any outboards were approved in the past.

    Inboards, due to the forward weight distribution, and big low end engine torque, pop up on a plane much faster than an outboard. Not as big a deal to an experienced skier it is a big deal when teaching a novice. Since a lot of these boats were used to teach when they weren’t practicing for competition, there was an incentive outside of the competition world to use the layout.

    At the time that competition skiing was getting started, outboards were a lot less powerful and it would have taken two of them to be a decent ski boat. Not that there weren't boats like that available, but as others have noted the skier tends to pull the outboard boat around a lot more. Two 50’s on a 18 foot hull isn’t a sweet a ride compared to a V8 mounted in the middle. Mercury came out with the Mark 75 (a sixty hp six) in 1957, at which time competition water skiing had been a growing sport for a few years already using the inboard layout. In 1959 the first Masters water ski competition was held, and big outboards just weren’t popular with the ski crowd. A big V8 also has a lot of torque and the skier isn't going to slow the boat down as much, it will maintain a constant speed (critical in competition) a lot better than an lower powered outboard when the skier cuts hard.

    Finally, the wake of the inboard is a lot lower at skiing speeds, again a big advantage for competition where you want the wake to be low and consistent. With all of that weight aft, a twin engine outboard would throw a lot bigger wake at skiing speeds. Remember that while the skier is hauling through the slalom, the boat isn’t going that fast, so the wake produced at low and medium speeds is really important, and the aft CG of the outboard hurts that.

    Most all of the above has been mentioned in one way or another, but you have to look at the history too and it all comes into perspective. I’m not saying that you couldn’t do it with an outboard now but it would be a lot harder to do. Hydrodynes with twin outboards were used in some Midwest ski shows, but I don’t know if they were used for competition. The basic competition ski boat has been pretty much unchanged for a long time because it is very good for dragging a skier thru the course in a very straight line at a constant boat speed with a low and consistent wake.
     
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