lawn mower

Discussion in 'DIY Marinizing' started by boat, Nov 20, 2004.

  1. boat
    Joined: Oct 2004
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    Location: aus

    boat Junior Member

    Dose any one know a way of adapting a lawn mower motor in to an inboard motor
     
  2. tom kane
    Joined: Nov 2003
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    Location: Hamilton.New Zealand.

    tom kane Senior Member

    This image may be of interest to you.The drive unit was made from a section of 4 inch galvanised pipe about 18 inches long with a plate welded about half way up so that when a hole was cut in the keelson the tube was sealed to keelson.Two water pump bearing from a vehicle were welded top and bottom and a chain connected the two bearings which had chain sprocket attached.
    An exhaust pipe went down inside of the tube and welded at the bottom.The drive was used as a tractor propeller and was very good in this dingy with a lot of rocker in the rear end.A MK 10 Villers engine of 1 HP drove to a pully to the top bearing and the weight of the motor kept tension on the drive belt and could be used as a clutch by raising the motor.
     

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  3. bsmit24
    Joined: Mar 2005
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    Location: Louisiana

    bsmit24 Junior Member

    I have a small 14' fiberglass skiff that I would like to try something like that on. Do you have any other info about the setup or a website where I could look at someother pic/drawings

    Thanks
    Brian
     
  4. marshmat
    Joined: Apr 2005
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    marshmat Senior Member

    The big problem here is that a lawnmower engine has a vertical shaft, a boat propshaft is usually horizontal. To use the mower engine to turn a prop, there needs to be a 90-degree gearbox somewhere. Running a mower engine turned on its side will do some pretty hefty damage to its innards. You can easily adapt them to outboards; Briggs&Stratton even sells one of their mower engines with an outboard leg and bracket attached. The only production vertical-shaft inboards I've ever seen are Merc O/B powerheads tacked onto jet drives.

    No real reason why you couldn't try though. Perhaps use the lower gearcase of an old outboard, bolt it on the undersde of the hull with the shaft coming up through the hull, stick the mower motor on top of that? Just a thought....
     
  5. bsmit24
    Joined: Mar 2005
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    Location: Louisiana

    bsmit24 Junior Member

    I think Glen L has a conversion for a vertical shaft and an old outboard leg. It uses pulleys so that you can run a larger prop. I might try that if all else fails. I could not find a sutible prop that would work.

    But I have an 12.5hp horizontal shaft that I wanted to use.
     
  6. kmorin
    Joined: Apr 2005
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    Location: Alaska

    kmorin Senior Member

    marinized lawn mower engines

    bsmit24,
    about 20 some years ago there were ads in the back of National Fisherman and some other marine periodicals that offered various 'designs' to use Briggs engines both horizontal and vertical in boats.

    In each case I think these applications used cog belts or rubber toothed belts like timing belts because they'll transmitt hundreds of horse power and are tolerant of line up error. I saw one of the brochures and it essentially used off the shelf pulley wheels and bulkhead mounted bearings with common shaft hubs to reduce the full speed RPM down to shaft speed.

    The horizontal applications arranged the engine above the shaft and drove the shaft by and offset cog belt. The shaft pushed and pulled on a double cone bulkhead mounted bearing -like Fafnir makes.

    One design used the bottom end of an old outboard by cutting through the aluminum casting of the leg and tapping the face of the casting for a bearing that stablized the cut off vertical shaft. This had a vertical shaft engine coupled to the top and the leg could not pivot- it was fixed like a keel boat.

    I recall the designs were a few dollars each and were mailed from Maine or somewhere in the NE. They were plenty innovative and looked like they'd move a small skiff.

    One very interesting application was a centrifugal pump that was made by welding some sections of large diameter pipe to a set of round plates and included a means to drill out the plates and balance the entire impeller. This unit was powered by vertical shaft motors and was teh pump housing was bolted to the bottom of an aluminum riveted skiff about 14' long. The tiller moved a "jet nozzle" and the tiller rod bolted to the transom of the skiff.

    I have no idea if these pamphlets are still for sale or who the author/inventor was. They made no provision for exhaust cooling that I recall.

    Sounds like a fun project, shouldn't be too hard to rig up -I think the shaft log & seals for a conventional shaft arrangement would be the most complicated in a small boat. If you used parts of an old outboard then most of the running gear is already marined.

    Cheers,
    kmorin
     
  7. Machnumber2
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    Location: Mission Viejo, Ca

    Machnumber2 Junior Member

  8. Machnumber2
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    Location: Mission Viejo, Ca

    Machnumber2 Junior Member

  9. PowerTech
    Joined: Feb 2005
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    Location: FL,Keys

    PowerTech Senior Member

  10. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    This probably isn't what you meant but it's sort of an inboard and it did work.
     

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  11. tom kane
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    Location: Hamilton.New Zealand.

    tom kane Senior Member

    Hey that is great,and you should see some of the modern concepts for high speed work.
     
  12. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    If you were referring to paddlewheels, I would like to see anything new about them. Sam
     
  13. tom kane
    Joined: Nov 2003
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    Location: Hamilton.New Zealand.

    tom kane Senior Member

    Hi Sam,if you take a look at the thread Modern paddelwheels some ideas abound.
     
  14. Machnumber2
    Joined: May 2004
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    Location: Mission Viejo, Ca

    Machnumber2 Junior Member

    That is fantastic, nice work! How fast does it go, and do you have trouble with the belt slipping?
     

  15. tom kane
    Joined: Nov 2003
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    Location: Hamilton.New Zealand.

    tom kane Senior Member

    If you use all of the outboard as is,that is the motor,leg and gearbox there are no belts to slip.A simple model goes well and can grind through the shallows.Add wheels to the boat there is more fun.A fast model would need to be well engineered and there is a lot to learn with this type of propulsion.
     
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