2-stroke lawnmower engine questions

Discussion in '2-Stroke Engines' started by keatonx, Apr 4, 2012.

  1. keatonx

    keatonx Member

    Hi. I have a 2-stroke tecumseh lawnmower engine (commercial 4hp) that I want to put on one of those mini inflatable boats that you can buy for 10 bucks. It'l be pretty insane! No, it isn't going on a motoredbike, but hey, i'm already on here!
    The angle I will need to run the engine at is about 35 degrees and i'm wondering if the bowl-type carb will work alright at this angle. Also, the lawnmower blade acts as a flywheel, and i heard without it the engine will run rough and kick back. Is this true on a 2 stroke lawnmower, and can it be avoided? (i heard getting a cast iron flywheel as opposed to the aluminum one helps, but i don't want to have to buy anything)

    I am planning on using an angle gear box from off a weed eater's straight shaft but I don't know if it will hold up. The shaft that leads to it is only about 1/4 inch in diameter, and the mower engine shaft is about 1 inch in diameter! Hovever, I might drill a hole in the center of the engine shaft and slip a peice of the 1/4 inch straight shaft into it so only the square end that fits into the gearbox is exposed

  2. vermhot

    vermhot Member

    Sounds like a lot of work that might not work !! To me ,but hey your time and cash !!!!
  3. vermhot

    vermhot Member

    I sa pose it could be done , you got alot of time and green ,you can do anything man !!!!
  4. HeadSmess

    HeadSmess Well-Known Member

    carby, should be ok, depends on which way its tilted really. and if its on a "clamp" mount, then...no issues whatsoever, just mount the motor so you can spin the carb to "level"

    brushcutter gearbox...depends on the brand. and location. underwater....no. but "commercial" quality brushcutters...yet to find one with the box broken before the engine gives in...

    it may be 1/4 inch but its usually hardened and tempered!

    good luck drilling an ACCURATE hole in your crankshaft without a lathe ;)

    flywheel...check the main fan/magneto for size... thats also a flywheel. may need some extra inertia, may not..

    how are you ATTACHING all of this to an inflatable boat?
  5. motorpsycho

    motorpsycho Active Member

    i never knew that tecumseh made a 2 stroke.
  6. Al.Fisherman

    Al.Fisherman Active Member

    Yes they did/do.
  7. vermhot

    vermhot Member

    My Strike Master Ice-auger has one on it !!!!
  8. BigBlue

    BigBlue Active Member


    Google "weedeater outboard" and you should come up with some ideas. I think the 4hp would be too much for the weedeater assembly. Might be too much weight in the back of the boat. Looking at the below forum, it might weigh 15lbs?

    Years ago, I had a 2 stroke 7.5hp air-cooled outboard motor that was a lot lighter than a water-cooled outboard. I had a lawn equipment mechanic that converted a water-cooled outboard to an air-cooled, using a lawn mower engine.

    A possible solution might be to install a compression release valve to the engine head to reduce kick-back. Never did it and don't know if it would work or not.

    http://www.baileysonline.com/itemdetail.asp?item=QH 50371 5301

    Here's a forum that talks about a 4hp Tecumseh:

    Good Luck,

    AKA: BigBlue
  9. keatonx

    keatonx Member

    I've placed a big rectangle of plywood under the boat, with a foot of extra plywood sticking out the back, where the engine will be. there is another, smaller rectangle of plywood that sits inside of the tube, where your body goes. The 2 pieces are just screwed together and sandwitch the bottom of the boat between them.

    I've ended up building a simple centrifugal jet drive for the boat using half of a paint can for the impeller housing, and a flattened steel pipe for the impeller, which spins inside the paint can. the centrifugal force forces the swirling water out of a (soup-can) pipe that leads out of the side of the can. I think this is the easier option.
    (and if I did need to drill that hole in the crankshaft, could I start the engine and press a drill bit against the spinning crankshaft and find the perfect center?)

    I don't think lawnmower engines have magnetos, just an ignition coil, flywheel, and maybe some points.

    Sorry, I dont know what you mean by a main fan.

    I just got a briggs 5hp 4 stroke mower engine at a dump and got it fixed and running without a blade, but it didn't idle too slow, and when I pushed the throttle to see how it revved ungoverned, it jerked a bit, then revved. And it kicked back. when I pulled the cord, it would yank it out of my hand and smash it off my ribs, which hurt enough that I wore a lifejacket for protection when I started it. BUT, this is a 4 stroke, which has 3 strokes that don't make power, so it might come with a bigger flywheel. MAYBE I could put it's flywheel on my 2 stroke engine, which has only 1 non-power stroke, to give it extra momentum.

    Anyways in a few weeks it will probably be finished.