Converting an Outboard to Diesel.

Discussion in 'Outboards' started by rustybarge, Aug 26, 2014.

  1. rustybarge
    Joined: Oct 2013
    Posts: 533
    Likes: 3, Points: 18, Legacy Rep: 37
    Location: Ireland

    rustybarge Cheetah 25' Powercat.

    ...those Harley chopper conversions cost at least $50k including the trick paintwork on the tank.:rolleyes:
     
  2. Moggy
    Joined: Feb 2011
    Posts: 181
    Likes: 8, Points: 0, Legacy Rep: 76
    Location: Somewhere else!

    Moggy Senior Member

  3. rustybarge
    Joined: Oct 2013
    Posts: 533
    Likes: 3, Points: 18, Legacy Rep: 37
    Location: Ireland

    rustybarge Cheetah 25' Powercat.

    Thanks Moggy,

    Love the 20hp chassis models because they use a 90 deg gearbox just like I was proposing: http://www.klaxondieseloutboards.com/category/outboards/lhseries/

    Are these the same as the Runsun Chinese models that Hastings Harry was investigating?

    Listening to the video they Seem to run smoothly; maybe a triple outboard setup hung off the back of a trawler to give 60 hp would work, and look very very cool.

    Love the long leg options......!!!! Wow, wow, wow......

    [​IMG]


    Basically I was thinking along the exactly the same lines as these OB's, but locating the Diesel engine on top of the 90 deg bevel gearbox as a 70hp Engine is going to be considerably heavier.

    So......
    The monster 557 v8 550hp use this engineering concept, and the Chinese 20hp Klaxon chassis design.........

    ....so why not a mid power design of around 100hp or less?
     
  4. waikikin
    Joined: Jan 2006
    Posts: 2,324
    Likes: 104, Points: 73, Legacy Rep: 871
    Location: Australia

    waikikin Senior Member

  5. rustybarge
    Joined: Oct 2013
    Posts: 533
    Likes: 3, Points: 18, Legacy Rep: 37
    Location: Ireland

    rustybarge Cheetah 25' Powercat.

    You needn't tell me, I already know I'm a genius at Photoshop....:D

    Rotate the bevel gearbox on the VW engine/gearbox into the down position where the red arrow is pointing.

    Dump all the gear cogs as the bevel output shaft is 1/1 to bring drive to the rear diff ( I think?)

    Simple, already engineered to be strong, off the shelf, spares available.;)


    [​IMG]
     
  6. rustybarge
    Joined: Oct 2013
    Posts: 533
    Likes: 3, Points: 18, Legacy Rep: 37
    Location: Ireland

    rustybarge Cheetah 25' Powercat.

    Thanks Jeff , some very interesting solutions, and more votes for a 90 deg gearbox......:D:D:D

    [​IMG]

    Love it.
    This idea would be very easy to fabricate for a larger engine, saving $$$$.

    Those slasher gearboxes look very strong and designed for continuous duty.
     
  7. rustybarge
    Joined: Oct 2013
    Posts: 533
    Likes: 3, Points: 18, Legacy Rep: 37
    Location: Ireland

    rustybarge Cheetah 25' Powercat.

    The drive belt drive:
    [​IMG]

    My only criticism is that this presents a very big square box to the water flow: that's why this design uses a surface piercing propellor to keep the leg out of the water flow...
    [​IMG]
     
  8. rustybarge
    Joined: Oct 2013
    Posts: 533
    Likes: 3, Points: 18, Legacy Rep: 37
    Location: Ireland

    rustybarge Cheetah 25' Powercat.

    Sorry wasn't thinking straight ....

    Fantastic idea bringing the belt drive down to just the level of the bottom of the transom, where a big square box makes no difference as it's protected by the transom from the flow of water.

    ..No 90deg gearbox needed, as the horizontal engine crankshaft and the propellor stub shaft are both horizontal.

    Which means it might be possible to fabricate a standard sub-surface propellor setup. ( surface props are useless at pushing at slow speeds in a big trawler)
     
  9. waikikin
    Joined: Jan 2006
    Posts: 2,324
    Likes: 104, Points: 73, Legacy Rep: 871
    Location: Australia

    waikikin Senior Member

    If you're prepared to fabricate, a chain driven(ganged) might go ok, envisage a torpeedo shaped lower unit say a pipe with nose/tail cone, the nose cone carrying the shaft & thrust bearings forward, aft oil seals/stern bearing, the leg fabricated from 2 segments of large pipe, oil bath in lower end, steering a complication but maybe not required, tilting sideways centered around the input shaft........ would be interesting, esp if some one funded it;)

    Jeff
     
  10. rustybarge
    Joined: Oct 2013
    Posts: 533
    Likes: 3, Points: 18, Legacy Rep: 37
    Location: Ireland

    rustybarge Cheetah 25' Powercat.


    Nice idea.

    How about fabricating a big vertical box like on the gator, bolt a saildrive propellor unit/gearbox to the bottom of the box at the water level, bring drive down with big belt drive, mount engine as per gator.

    The advantage of this system is all you have to buy is a standard saildrive unit, disconnect the gearbox and small leg, fabricate big vertical box, bolt g'box and leg to bottom of box, fabricate frame for engine as per a Gator......
     
  11. rustybarge
    Joined: Oct 2013
    Posts: 533
    Likes: 3, Points: 18, Legacy Rep: 37
    Location: Ireland

    rustybarge Cheetah 25' Powercat.

    An out of the box solution like a saildrive sounds nice: everything is already sorted like the gearing, propellor size, correct transmission, reliable marine diesel already marinised.


    .....the big vertical box is not a very attractive engineering solution though!
     
  12. rustybarge
    Joined: Oct 2013
    Posts: 533
    Likes: 3, Points: 18, Legacy Rep: 37
    Location: Ireland

    rustybarge Cheetah 25' Powercat.

    Something like this, the g'box and saildrive leg bolted onto the bottom of the vertical box that houses the belt drive:

    [​IMG]
     
  13. rustybarge
    Joined: Oct 2013
    Posts: 533
    Likes: 3, Points: 18, Legacy Rep: 37
    Location: Ireland

    rustybarge Cheetah 25' Powercat.

    Ok getting back on track again.

    Looking at the VW gearbox, the input shaft indicated by the red arrow goes straight through to the end of the box where the 90 deg bevel gearbox bolts on (blue arrow.)

    So all the other gear cogs and shafts and the differential can be dumped to save weight, leaving a neat and simple 90 deg g'box.

    The clutch will not be needed, as I believe most big OB legs have a built in gear selector/neutral


    [​IMG]
     
  14. rustybarge
    Joined: Oct 2013
    Posts: 533
    Likes: 3, Points: 18, Legacy Rep: 37
    Location: Ireland

    rustybarge Cheetah 25' Powercat.

    Beaten to it......:D

    http://articles.maritimepropulsion.com/article/New-300hp-(224-kW)-Diesel-Outboard29225.aspx

    At the recent international defence exhibition and conference (DSEi) in London, a new lightweight diesel engine was on display. The British company Cox Powertrain Limited (http://www.coxpowertrain.com) is developing, together with Ricardo UK a modular, power dense engine with target output of 300 hp (224 kW) @ 4,000rpm from a 3.6 liter supercharged 2-stroke diesel engine, weighing 300 lbs (136 kg). Such a high power to weight ratio opens up a variety of application opportunities such as marine outboard motor and powered flight e.g. UAVs.

    [​IMG]
     

  15. WestVanHan
    Joined: Aug 2009
    Posts: 1,374
    Likes: 56, Points: 0, Legacy Rep: 746
    Location: Vancouver

    WestVanHan Not a Senior Member

    Nice,but $80k?

    Anyways no mention has been made of the diesel's stronger power pulses and the vibration.
    I'm guessing those alloy cases -designed for gas engines- will crack fairly quickly and the gears will spall.

    Look around here:
    http://www.alibaba.com/trade/search?fsb=y&IndexArea=product_en&CatId=&SearchText=diesel outboard

    I've imported lots of things from China-it's usually hit and miss. Some things are good,some are not. You can have the same engine and looking almost the same-but built by two manufacturers-one is crap,the other good.

    Anyways gents the sockeye are running up the coast, wife and I are out to catch a mess of salmon-the canner and smoker await.

    Nice place BTW rusty..I love driving around Europe and seeing places like that.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.