Ski boat project questions

Discussion in 'Powerboats' started by aussiebushman, Sep 22, 2012.

  1. tunnels

    tunnels Previous Member

    Because i have my motor set back away450mm plus the bracket so is over 500mm back the motor is raised up 25mm and is perfect it could go twice that if i was a real speed freak . i have a small keel about 30 mm deep but it finishs away down the hull 1.500mm from the transom !i have done stage one on my boat and when i get time i want to do stage two which is major modifications to change the hull shape thats all completely possible . Increase the vee slightly and intoduce two 180mm wide strakes plus a flat at the rear of the hull then will have almost 500mm os flat are combined to pick up the hull into planning mode very quickly and that where it will stay most of the time ,its not a light boat so sits well in the water and the power trim is sensitive and easy to trim for a nice comfortable ride at almost any speed even flat out . head wind and you can feel it wants to lift bo back off an little tail wind and its all out and going for it !!.
    25 inch outboards are quite commom is some countries . a lot of the aluminium boat manufactures use then on fishing boats and some of there pleasure boats as well Just be a little carefull the base size of the bracket where bolts to the transom is slightly bigger on the dedicated 25 inch motors ,something to take into account . There used to be spacers kits you can get to change 20 to 25 on some outboards . Mercury and omc just fitted the spacer . Yamaha was 100% dedicated with there 25 inch long shaft .
    Just that extra height makes a lot of differance and the motor cover hardly ever gets wet with spray at all . the engine height of 10m to 12 mm above the level of the bottom of the hull is good !!, makes it lighter on the steering , specially with cable push pull !!, makes it get up and go quicker (hole shot ) and cuts down dramaticly on the amount of splash and spray coming from the leg where the water stricks it after it leaves the transom. depending on the transom angle the motor could be further back the more angle its racked back !10mm is about the normal for standard set up and a good starting point . Used to fit out boards to all the boats we were making and was where we started , most never had to be shifted .
    Its better to load the boat slightly towards the after end and use the trim to level it ! when you take off trim the outboard in !!, push the throttle down and go then trim up as you pick up speed !,no two boats are ever the same and all behave differantly . Another thing to watch for is lack or play in the steering cable can scare the pants off you if the outboard suddenly movers slightly and the boat want to change dirrection . I fitted a hydralic system complete and would never ever use anything less again . even at over 60 mph plus its one finger steering its so light and easy to steer the kits have everythin and the rams are fitted to the motor so there not even a fraction of slack any where .
    Set up and Fine tuning make the differance between being a pleasure to drive and never having to fight with the wheel and a chore and it beeing a semi battle every where you go .
    Its like driving a front wheel drive car with one bald tyre on the front and one good tyre . Why battle with it when there no need to ?? :D:p
     

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  2. aussiebushman
    Joined: Oct 2009
    Posts: 268
    Likes: 18, Points: 18, Legacy Rep: 132
    Location: Taralga NSW

    aussiebushman Innovator

    Thanks - you guys are a wealth of good information. I'm collecting the hull at the end of next week, then will take measurements and more pictures for your suggestions. Your comments on the motor, mount, cutout are invaluable as they will stop me from doing anything silly with the deck framing and internal structure.

    You should be interested in the proposed decking method - quarter sawn 50mm X 19 mm Paulownia beams, 4 mm marine ply cover just as a bonding surface - all West system epoxy coated both sides, then a laid deck of 50 mm New Guinea Rosewood strakes with 10 mm Paulownia strips between them - similar to the pictures here. These timbers are superb, the NG Rosewood is as durable as teak and the Paulownia I know well because the tri has been strip planked in it.

    It does not stop me planning the skiboat project, but it may not start for some time. I only just launched the 22' tri and the mast is not even up yet (due to the massive wind on launch day) so I want to get that sorted and sailing first. (Picture of tri on mooring is here for those who might not have seen my post in the multihulls forum)

    Keep it coming!

    Alan
     

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  3. tunnels

    tunnels Previous Member

    Watch this space !!

    If you going o do a laid fancy deck i will find a sight where theres lots of things to look at !! as a out board boat it can look really classie !!! some of the old woodies from the 30s 40s 50s we really nice i use to make model boats when i was a school and get all the thin off cuts of wood from a guy across the road from our house he used to build boats !:p:D:p.
     
  4. aussiebushman
    Joined: Oct 2009
    Posts: 268
    Likes: 18, Points: 18, Legacy Rep: 132
    Location: Taralga NSW

    aussiebushman Innovator

    Try this one - http://www.classicwoodenboatplans.com/ it should be an inspiration to us all, though I do not kid myself that I have the skill to get even close.I'll just take my time over it.

    On problem I may confront is available scantling sizes. One really helpful guy in the trade in Sydney applauded my selection of the NG Rosewood, but may not be able to supply wide boards. The Paulownia is easier because it is available in 255 X 55 planks and you will know there are no knots and ripping is simple on a bench saw.

    Cheers

    Alan
     
  5. tunnels

    tunnels Previous Member

    Something to keep you busy looking at !!

    http://www.craigstrike.com/ nice pictures !!

    I used to cruise on this site for hours in years gone past http://www.classicboat.com/boats.htm


    http://www.vintagemarine.com/sale.html

    Probably seen this a 100 times
    http://www.glen-l.com/designs/hankinson/buildingmahogrunabouts.html

    a couple od really nice classic outboard boats
    http://features.boats.com/boat-content/2010/09/raveau-restoration-a-classic-runabout-returns/


    you could get some good info from this site
    http://www.woodshop102.com/49.html

    something close to home of interest maybe
    http://board.net.au/yabbse/index.php

    wow this site i never seen before and will spend sometime tomorrow . its got a hord of stuff on it and lots good stuff in the last half
    http://www.portcarlingboats.com/WoodenBoats.htm

    Hope you enjoy because i did just finding !!! :p:D:p
     
  6. pistnbroke
    Joined: Jan 2009
    Posts: 1,405
    Likes: 33, Points: 48, Legacy Rep: 404
    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    I think a 115 4 st may be a bit heavy ..if it floats put it in the swimming pool and put some weights in it and on the transom ..a 90 hp two stroke may be the way to go ..it will certainly do 30 kts with the 90
     
  7. tunnels

    tunnels Previous Member

    A yamaha 2 stroke vee 4 is a good motor , has oil injection and its very reliable . the only time its smokes is when its been sitting for a while like over night . one puff of smoke when i start up in the morning and thats my lot for the whole day .
    The 115 hp and 90 hp are the same outboard basicly on some brands !!! The yamaha 90 2 STROKE is a 3 cylinder or 4 cylinder if you can find one so its possibly the lightest of the collection .:D
     
  8. Frosty

    Frosty Previous Member

    It depends what skiing your going to do --if you going to do some serious mono skiing on a slalom course you will pull that boat and its engine all over the place. Yes it may appear to go fast enough in a straight line but a good mono skiier will pull many times his own weight . Barefoot cranks this up some more and 200Hp will be required.

    For some serious work the Master craft has been king for decades.
     
  9. aussiebushman
    Joined: Oct 2009
    Posts: 268
    Likes: 18, Points: 18, Legacy Rep: 132
    Location: Taralga NSW

    aussiebushman Innovator

    Actually Frosty, the project is mostly a way of keeping me sane because I live in the mountains on a property and have a lot of boatbuilding experience (sailboats), the tools and the time. By nature I am a sailor and not at all interested in water skiing, or even breaking speed records. I will probably use the boat just for leisure for a season or so before selling it.

    If a buyer wants to break records, he can change the motor later at his own expense. From comments previously received, there is not much difference, if any, between the weight of a 90 and a 115 HP motor, but ultimately, the choice will depend on what is available as good second hand at a price I can afford, yet sufficient power to do, say 30 knots and convince a buyer it is a good package.

    I'm not dismissing your comments, but these are my objectives. If I get the finish right and the performance is reasonable, a sale will more than pay for the materials and my labour.

    Regards

    Alan
     
  10. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 471, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    It's hard to tell a lot from the photos presented, but 115 HP on that wouldn't be asking much of it, from what I can see. She appears to be a warped bottom with a modest amount of deadrise and a lean beam/length ration, all good for speed and supporting a 115 HP outboard.

    Prospective buyers don't want to have to add a new motor, but prefer to find one with the engine that produces excellent preformance, right out of the box. In this regard a 115 is a better choice.

    Originally setup for small block V8 HP preformance, a 115 is a bit weak kneed in comparison, though saving a few hundred pounds will offset this a bit. This is the type of boat that will likely do well with 200+ hp on her transom, so consider this when selecting the engine.

    Please provide the length, weight, waterline beam and transom beam and we'll can roughly see what she can actually handle. Simply put, the V8 would have produced 200+ HP in a 900+ pound package. A 200 HP 4 stroke outboard is about 500 pounds and a 115 about 400 pounds. With the fuel midship, she'll preform well with less HP, but don't go too far down, as it'll kill it's abilities.
     
  11. aussiebushman
    Joined: Oct 2009
    Posts: 268
    Likes: 18, Points: 18, Legacy Rep: 132
    Location: Taralga NSW

    aussiebushman Innovator

    Thanks Par

    As stated previously, I'm collecting the hull in a bit over a week and will get all the dimensions then.

    Regards

    Alan
     
  12. tunnels

    tunnels Previous Member

    Cant wait to see more pictures !!

    Possible to get some good pictures of everything ?? can help a lot side front transome inside and out all the inside !!!!etc etc the more the better . do some searching for a motor . The one i got is second hand and because its 25inch no one wanted it at the time !it had all the gizmos with it gauges and cables etc etc . ionly thing one day it wouldnt start no way so down to the local boat place and the guy fount the power pack was shot so got a second hand one and wow did it make a differance it had never go that good before so must have been on its way for a while . Because i live in china andony get home once a year i drown it with wd40 every where . One turn of the key last time in January it if fired up instantly with a little choke couldnt believe it been sitting for a whole year !! i like yamaha and most of the small power boat places i worked we always fitted Yamaha and when they went they never came back for any reason . hydralic steering with a big motor is heaven we have a auction site called trade me and i got the motor off there , later i found the kit for the steering and i found the old steering wheel just slipped straight on and did up the lock nut . Took about a hour to bleed the system twice after i let it all stand for10 minuts and let the bubbles surface . in 3 years i never had to do a thing to it . checked the oil and was the same each time . trouble free and lighter than a car to steer even at full out top speed . .
     
  13. aussiebushman
    Joined: Oct 2009
    Posts: 268
    Likes: 18, Points: 18, Legacy Rep: 132
    Location: Taralga NSW

    aussiebushman Innovator

    Maybe found an engine

    The engine search might just be over:

    150 hp mercury motor includes power head ,carbies,gearbox/25" leg,electrics,steering ,tilt and trim ,hydraulics,electric start,front controls ,also dvd workshop manual​

    Having plenty of time, reasonable mechanical skills but little money, this 150 Hp motor at $400 sound like just the ticket. It had a broken ring but no cylinder scoring and all the parts are there including the remotes. The leg alone is worth more than that

    Anyone want to tell me I'm mad? But then. I already knew that

    Alan
     
  14. tunnels

    tunnels Previous Member

    search and ye shell find !! theres a reason for things happening when they do ! i say Take it !! . what year ?? and its a 25inch as well just made to order !!. point to remember when you are doing the transom the 25 add more presure to the transom because of the extra length thats why i said a 50mm thick transom not 40 as was stated . make it strong and have no regrets . good for you !!have my vote !:D
     

  15. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 471, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    It's very rare to snap a ring and not scratch the crap out of the bore, suggesting someone isn't telling the truth. I wonder what else he's not being honest about. It sounds like a good deal, but I'd want to see the bore.

    Agreed 50 mm on the transom core is wise. The earlier 38 mm recommendation was understandably for the smaller engine.
     
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