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Thread: new guy looking for ideas

  1. #1
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    new guy looking for ideas

    Hi all,
    Looking for some info from you experienced mini-types, that have managed to survive the experiences!
    Im a saltwater fish-o-maniac, living on the forgotten coast of FL (NW, not panhandle) I have a fiberglass double hull jon boat that I salvaged from the dump, 15.5 X 48 where it counts, 16 gunnels,it weighs a ton well, more like 500 Lbs +.
    I needed a motor to replace an old 5.5 HP Evinrude. A friend gave me a 35 HP Rockwell JLO airboat motor, circa 1969-ish from his duckboat, the price was right (Im a homesteader on fixed income, SSI), so a couple months and some fiberglass and metal fabwork later, (I made a venturi cowl for the prop, it seems to help a bit). I put it in the water and started chasing the reds and trout. I absolutely love this crazy thing, but I only get about 6-7 MPH, It plows. The setup I have is great, casting deck up front, nice spacious flat interior, really stable in the water, but I fish the gulf, weather permitting. I range 1-3 miles out, when Im doing the flats, and inshore creeks. Id like to venture as far as 8 10 miles out, for the reefs and wrecks, but if a blow comes up, you really need to get off the water quick as you can.
    I know jon boats are not the ideal hull, but I cant afford the materials to build one from scratch, much as Id like to.
    So, what if I use an old 14 aluminum jon boat, split it down the middle, add 1 to bring it to 5 between the chines, & rework the bottom with 1/8, to get that smooth plane surface? I can dig up a couple hundred for 1/8 sheet, & some structural channel, & can scrounge up a redneck tig setup for my old Forney stick welder. Im not building a racer, but do you think I could get maybe 10-15MPH out of a hull like this, with this JLO direct drive pushing some unknown brand 42 wood/stainless prop? Average payload would be me and wife + gear, maybe 300Lbs (were small folks) I dont have grand aspirations of planing, would be great if it could, but I understand the physics are against me. I probably will try the jon boat as is, first, but

    If I were able to afford the materials, Id probably go for about 13.5 X 70 with 25 gunnels, (for 1-3wave height) with flotation styro in every conceivable nook and cranny. Any helpful input is welcome, and yes, I know Im crazy, cant help it!
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    Last edited by 3cells; 03-17-2018 at 06:01 AM.

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    Member yamahaulerG1's Avatar
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    Re: new guy looking for ideas

    The Jon boat will be a great improvement from what you have 14' works really well. And yes you can split a Jon boat and widen it out just takes some work. We used an old 12' Jon cut the middle out of out so we just had the sides and about 6" of the bottom because we cut out next to the first rib, then riveted a 4x12 sheet of .090 to the sides and 4 pieces of angle down the middle to make a 4x12 flat bottom jon boat
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    Re: new guy looking for ideas

    This boat started out with an 0-42 with 1.69:1 reduction, then went to a Honda 20hp direct drive, and now a 32hp propane powered generac with 4 blade ultra prop and it runs about 20mph with 2 ppl, a cooler and, 2 bbq grill tanks. So it should be a close comparison to what you want.

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    Re: new guy looking for ideas

    thanks so much for the reply! and the encouragement. The pics are great!

    How do you waterproof the rivets? rubber washers or weld over them? does it add much cumulative drag? Thanks again for your kindness, I tend to be a little too "creative" for some. rivet to the rails, & weld the seams? butt joint or overlap?

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    Member yamahaulerG1's Avatar
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    Re: new guy looking for ideas

    We over lapped the sheet over the original bottom about 6" the whole way. When I cut out the ribs it left about 6" of the bottom on the two pieces. For the transom we found a piece of aluminum in the scrap pile just wide enough with a1.5" bend at the bottom at the metal shop where we bought the 4x12 sheet. We sealed it with butyl caulk between the sheets, and riveted it with rounded head aircraft rivets using a cut air chisel and half a window weight to back it up the rivets don't leak anywhere with no sealing and we were worried about the drag but you can't even tell there is 1000 rivet heads on the bottom. We didn't weld any aluminum on that hull, we did stick it together with self tapping screws to help hold it in place. We riveted two rows down the seams 1"x1" apart on a staggered pattern. We didn't follow any plans just guessing and hoping, we had never used an aircraft rivet before this and didn't have any real skills. It was just two of us that built it in our spare time after work.

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    Re: new guy looking for ideas

    I hadn't thought of just using rivets, it would make the whole project quicker and more do-able, I like it!
    Did you beef up the transom? My setup actually mounts on the transom, and the rear bench, so I had to reinforce both, but I could take a cue from the different rigging's I've seen here, & maybe lighten things up at the same time. When folks are talking EMT for rigging, am I assuming we're talking aluminum & tig welding? Or actual thin wall steel & brazing?
    Thanks again for this golden info! here in Dixie county, nobody's ever seen an airboat smaller than about 300HP, so I'm not getting much usable info locally.

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    Member yamahaulerG1's Avatar
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    Re: new guy looking for ideas

    I have had the same problem here everyone has a big airboat and thinks anything smaller then 150hp is a kids toy. And when we say emt it is 1/2" electrical conduit from the hardware store. It's very light and easy to work with and plenty strong enough if you brace it the right way. My first airboat i brazed the rigging with coat hangars and brass rods. Now i just use the $90 flux core welder from harbor freight it welds the emt nicely just turn the wire speed up and move fast so it don't burn though. But I would build a new lighter stand because weight is everything. Also beefing up the transom will create even more weight in the back. To save time try to save as much of the rigging you have now cut off what you don't need and just basically weld legs on it to brace it to the bottom of another boat.

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    Re: new guy looking for ideas

    really helpful ideas,thanks again!
    This project just gets more do-able! I remember my dad teaching me to braze, we used coat hangers and dipped the hot end in Boraxo dampened into a paste, for flux. I was a general contractor in CA for a few years, and I still have 1/2 & 3/4" conduit benders. Come to think of it, I've used them to make some bike trailers!
    Seeing as I'll have all those handy 1 1/2" rails on the deck for attachment, I REALLY, REALLY, need to re-think the rigging. The other builds I'm seeing are giving me ideas to go all-around lighter. Being unfamiliar with air-boats,I've had nightmare visions of having a running airplane motor chasing me around inside of a small box on the gulf, so I've used way too much steel angle iron! the one thing I do want to retain is the locking screw adjustment for motor/fan angle, really helpful for us experimental types. my prop is directly above the transom now, does that work on an aluminum hull too? I'm thinking weight distribution.
    Yeah, my neighbor across the road has a caddie V-8 on his, pushing I believe he said close to 700HP at the prop. (Wow, and He only uses it a couple times a year) He trailered it over to his daughters a while back to get some tree stumps and trimmings to burn a little better, it was hilarious, and real effective! a 10' X 10' pile reduced to fine ash in about 2 hours. That's why they call this the redneck riviera. I wouldn't live anywhere else! Thanks again!!

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    Re: new guy looking for ideas

    First i would rethink going a mile out in a Jon boat no matter what motor was on it. Yes weight distribution is very important you want be balanced that's why most airboats the motor is forward a few inches. Also it's funny you talk about using it to burn that's how we got rid the hurricane debris back the airboat up to the pile and keep feeding it with the excavator it was like a furnace burning huge tree stumps in no time at all
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    Re: new guy looking for ideas

    they work really well for fanning barbecues too!
    I will probably get moving on this project this week, I'll keep you posted, with some progress pics, here's one of my little friends!
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    Re: new guy looking for ideas

    Nice one, I am also about to rebuild my mine. I noticed the main support is cracked on my motor stand. I'll be looking forward to seeing your progress. I'll try to get a few pics of mine while i work on it.

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    Re: new guy looking for ideas

    question on your motor, is it direct drive?
    if i am not mistaken this motor is similar to my Cuyuna 460F45 engine, with the 2 carbs i am getting 45hp. but to reach that my rpm's are at 5500. and so i have a gear box to keep the prop speed in check.
    if it is direct drive, what RPM are you running it at?
    from the pictures that you posted it is hard to tell what kind of drive you have.
    with an direct drive system, you are limited to how many rpm's your prop is rated for. if it is only rated for 2500 rpm's.
    from looking at 2 stroke power curves, of motors from this era. at 2500 to 3000 rpm's, i wouldn't think you are even at the 15hp mark.
    just some questions, that i have been thinking about.
    please post some closer pictures of the motor & prop.
    thanks
    i located a web page that Kansas University submitted on the cuyuna 430 motor, back in 1983, it has a PDF file that contains all of the research they found. (pretty big one.) it looked like they used a direct drive prop, for the rpm's maxed out at 2810. but they were able to manipulate the data to obtain thrust coefficient, power coefficient, shaft horse power, an d shaft specific fuel consumption. . i am going to spend some time looking at this, and see if I have any means to incorporate this and use it for my own research. but at max rpm's.
    https://ntrs.nasa.gov/search.jsp?R=19840008111
    Last edited by Bart; 03-23-2018 at 07:17 PM.

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    Re: new guy looking for ideas

    Yes, it's a direct drive JLO rockwell 440-2. / 42" prop. / single carb. It's rated 35 HP @ 6750. I have no idea what rpm I'm maxing. I made the fan cage into a venturi cowl, to boost the thrust, but I have no way of measuring that either. After several weeks of rigging, i finally got it on the water and have been using as is, for life, liberty, and pursuit of redfish. I'm open for suggestions. a tach that will work on a magneto ignition, that's dirt simple and cheap would be great, any ideas?
    here's some pics of the setup
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    Junior Member Bart's Avatar
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    Re: new guy looking for ideas

    that is a nice motor, just detuned from what I have. a few of the others on this forum have ran motors similar to this,
    yes the motor can max out at 6700 rpm's, but you really don't want to run it wide open for to long of period.
    but the props cannot handle that rpm. the prop acts as an governor, to keep the rpm's in check. you will have to check with the prop manufacture to see what its recommended rpm is.
    the electric start is nice. if you skim though my post in the builds another project to play with. you will see where i am building 2 different motors a 084, and the cuyuna, and i talked about many of the questions that you have mentioned.
    also an simpler way is type in the word cuyuna in the search block, and it will pull up all the posts that reference that word.
    it just will take time to go through and see what others have posted.
    when searching the web, you can reference JLO, 2SI, or Cuyuna, for what ever reason, all 3 of these brands can interchange parts. and you will pull up many useful ideas. yahoo has some groups that have these engines in ultralights, also. https://groups.yahoo.com/neo/groups/FLY-UL/info
    what is the oil mix ratio that you are using?
    as far as places that can help you figure out redrive options http://j-birdengines.com/ might be one of your better options. and as far as any thing for the motor, look at http://zdenterprises.net/2055054.html

    your motor is the first that i have seen that has electric start with out a gear box, and i have only seen one motor on ebay that had a set up like mine, with the ring gear in a case and a gear box on the other side. but it take time to look and see what all is out there, and what is available. for this older style of motor.
    not to drive you away form this motor, but keep your mind open, if you are set on 2 strokes, a couple of years ago, one on this forum "rollbar" came across an gentleman selling an ultralight with motor for under 1000.00. it had the rotax 582, gearbox and prop.
    but visit with venders, and look around to see what is available. what you have is a good setup. but with out an redrive. you can't use the motor to its full potential. and you never want to over rev the prop.
    something else to look at is the exhaust. from what little i see, it looks like somebody set it up to run like a 4 stroke exhaust. which really can detune the motor.
    as you take time put some more pictures. i am not trying to detract or diss on what you have, but i have played with my motor for a couple of years now and have spent a lot of time looking for spare parts. to have on hand. and these old motors can be fun to say the least in finding the right set up that will work for what you have.
    but for me it is the journey, that i enjoy the most. hope that some of this can help you out.

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    Re: new guy looking for ideas

    I didn't think anything about it being two stroke and direct drive. That motor does have much more to give. You should get a tach and check your rpms search eBay for "digital tach" and you can find them for less then $10 a wire wraps around the spark plug wire and gives you a reading they have a few settings for different types of motors 4 strokes, and 2 strokes it's real easy to use. Hopefully it's right at 3000rpm so at least your getting all you can with it direct drive.

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    Re: new guy looking for ideas

    i was going through all my pictures and notes, and having fun trying to find what i wrote down about wiring up the tach. tonight i will take pictures of what i did. pictures help out a lot. but from what i seen in your pictures, your wiring may be an older style. but it should be similar.
    i used 2 different tachs on mine, an Tiny tach, and a Farina. just to verify what rpm's i had. but i will get to you how i wired them up.
    just a note about the ultra prop that i was using. the motor came with a 3 to 1 ratio gear box. the prop had 14 degree blocks on it. (i think) but with this set up, my rpm's were maxing out at 1/2 to 3/4 throttle. the only option i had would be to install 18 degree blocks. this would create more drag, and might bring the rpm's in check. but i had also picked up an other gearbox that had 2.65 to 1 ratio. so i installed that. this brought my rpm's down to around 6000 at full throttle. i ended up changing my pitch blocks one size. and this dialed in my rpm's to what I was looking for.
    now that i am seeing yours, it has got me thinking about spare parts again. about the only part that i am missing a spare on, is the fly wheel shroud. i have only seen one of these for sale on Ebay in the last 3 years and that was on a 3 cylinder cuyuna motor, ( this set up would have got me a 70 horse motor, but how many do i need) anyway now i am thinking of taking it off and making a CAD drawing of it. to have on file. just in case something happens to it down the road and i need to fab up a new one. these projects never end
    the second picture of of the exhaust set up. the 2 stroke motor exhaust needs to go into an expansion chamber to create some back pressure, this creates an scavenge effect, which with out it. the motor really doesn't work to well. they made 3 different styles of exhaust. and the one i have allegedly is the most efficient. below is an example of how it works, and the pipe needs to be tuned the the motor
    http://2strokeengine.net/2strokeengi...eanimation.php
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    Last edited by Bart; 03-24-2018 at 11:31 AM.

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    Re: new guy looking for ideas

    I'm running a 40 - 1 mix, and the exhaust says "tuned exhaust" but it looks suspiciously like every other car exhaust I've ever seen, but who knows? I'm looking for a tach, & will post when I can get a max RPM. The motor was out of a snowmobile, then adapted to a duck hunters boat, so there's all kinds of surprises. someone has been into the wiring, and ran 2 extra magneto wires for future reference, I guess. They're capped off for the time being.

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    Re: new guy looking for ideas

    Just a for what it's worth. A typical airplane propellor runs about 600 mph tip speed at red line. You should be able to run 4800 rpm for the same tip speed, and the 2 stokes normally need to turn at the rated rpm not to overheat. A clinder head temperature guage (snowmobiles used them) may be a good investment. Lots of variables and noise can dictate changes. Good luck continuing. Mike

  19. #19
    Member yamahaulerG1's Avatar
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    Re: new guy looking for ideas

    While you are right about tip speed that don't mean that it is safe to turn an old prop that fast. It is an ear killer and most props are not designed to efficiently push air at that speed. I had a 24"wood prop made with 20 layers and built a Honda 5.5 that would turn it 5000rpm on a 10ft Jon boat. I've never tried Arrowprops high speed props $$$ but i wouldn't try it with a regular prop. In shallow water it was about 20mph but the last 1000 rpm didn't really make much of a difference and a head wind would still keep it from getting on plane.

  20. #20
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    Re: new guy looking for ideas

    attached are a couple of pictures on how I wired up the Tiny Tach and the Farina tach
    when i installed the tiny tach. it was jumping all over the place when i had the red wire rapped around just one of the spark plugs, after visiting with the manufacture, they recommended to try leaving an 4" gap and rap the other spark plug wire also. this worked and solved the problem
    the tiny tach has 2 wires , red is rapped around the spark plug wire, and white is to ground, also with the tiny tach they have an internal battery that lasts only 3 to 5 years. then you need to replace the whole unit. ( there are some web pages that talk about splitting open the housing and swap out the coin battery, but i haven't tried that yet.)
    the Farina tach. one wire is tied into the kill wire coming off the coil. and then is grounded from another terminal on the back of the tach.
    both of these are very simple to install.
    my personal preference is the larger dial gauge tach. i can look down and know where it is reading. as for the tiny tach. it cost around 45 dollars, i didn't buy the cheap knockoff brand. i have found out from past, that when a deal is to good to be true, it usually is. and you have no guarantee on how long the battery will last in the cheaper ones.
    also I found out last year when getting mine dialed in, with out an tach. you are wasting time, and could damaged more than you bargain for, if you are overreving the recommended prop speed. below is a link off of my build page that lets you see the difference when looking at the 2 tachs side by side. and how it helped my get my prop adjusted to govern the motor to the correct rpm's
    http://miniairboatassoc.com/forum/sh...lay-with/page7

    the oil ratio is good, what kind of oil are you using?
    back in the 60's they used oil that had a TC2 rating, now the oil has TC3 rating, and i am using synthetic oil that i also use for my snowmachines.
    so I am going above and beyond what the manufacture has recommended. yes it costs a little more 40 to 50 dollars a gallon, but using the best and latest quality of 2 stroke oil, gives me a piece of mind. for i have very fond memories of playing on snowmachines back in the 70's that you would wrench on them for 10 hours and get a 10 minute ride out of it. so it is worth it to have a good quality tach, and pyro gauges to help chase down the demons on these old motors.

    another thought, the biggest problem that i had last summer was getting both cylinder running with close to the same pyro temps. when you look at the temp gauges on my link you will see one is reading 0 while the other is at 700 degrees. i chased this monkey for most of the summer, changing out jets, neeldle jets, carb slides, and everything to try to get them close, and nothing i did would was working. i would think i adjusted it, and it was looking good. but after an 1/2 hour of playing it would start cutting out and running rich again. finally i looked at the choke relief setting. one of my choke cables was not adjust correctly, and was allowing just a little rich mixture, what a pain, i spent over a month chasing my tail on that one.
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    Last edited by Bart; 03-25-2018 at 01:02 PM.

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