Weed eater engine conversion

always better to have a clutch particularly if you have no F N R ..you may need to tweak the prop for a little less pitch particularly for your early test ...if it had a water pump take that out as it puts on a big load .

 

I got the idea for the open shaft from looking at designs posted on this thread. I ran through some thick weeds as a test and the motor pulled through strong.

With the bushings, I used a strip of aluminum to secure the bushing, then drilled/tapped through both the aluminum and the bushing.

I haven't had any problems with heat yet, but I haven't run the motor for more than 10 minutes.

The motor is about 48" long. It could be longer, but when I get in the boat it's submerged enough to provide good thrust.

 

100% for the clutch

I've made and used both and the motor with the clutch is the way to go. Note t5hat not all small motor clutches are the same. When I built a mud motor from a 31 cc Bolens I don't think the clutch would have held up and it smelled something awful after only using for a short period of time. The next motor built with a 52 cc motor came with a much heavier duty clutch. I've run that for a season and a half and the clutch looks brand new.

The saftey factor is what makes me desire a clutch. Those small motors, when running, can turn around on you meaning if you are walking with the boat and the motor is running, the back end can become the front end and that spinning prop would cause some serious damage. Had it happen more than once and boy was I glad I had a clutch.

For what it is worth.

MArk

 

wow! excellent replies. i definitely agree, for safety and convenience sake, a clutch is...well...clutch. (sorry) maybe i can bring the clutch down to a mower shop and match the input to something a little more substantial.

the water pump impeller creating drag was not so obvious. unless i decide a rooster tail is necessary at 2mph, i'll be sure to remove those "extra" parts.

thanks Mark Wo and pistnbroke.

 

remember that the trick of mating an old outboard leg to a new engine is to use the end of the old crankshaft to mate the splines of the lower unit shaft to the new engine .....ie chop off end of crankshaft and weld /turn to suit...

 

pistnbroke,

sadly, i do not have the power head to put on the chopping block. next week i should have some time to post pictures of the clutch output and lower unit drive shaft input. i will swill a few cold ones and contemplate the mating of the two.

i used to work as a second rate machinist for a window shade company. there i learned how to use a Bridgeport and a lathe. however, i have neither at my disposal. i might have to contract the weld or machining out to some local outfit. we shall see.

your comments are appreciated!

 

i put a prop for a 5.5 hp scavenger mud motor on my 5to1 reduction motor. i was impressed i had the power to pull it. given i have done a few hp mods to my engine but it handeled the prop very well. i got about the same speed as i did with the 11 inch trolling motor prop but can run in 3" less water and keep the prop submerged. the engine will handle the prop digging in hard sand bottom as long as you can keep the prop from walking around the boat. i built this motor for an otter 1200 but have been running it on a 1436 jon because i still havent got the otter. coming on 4 weeks waiting for it.

 

hello all, im new here. i ran across this thread and really learned a lot. Has anybody heard anything from paraprop about getting one of those longtails?

 

Look back a couple opf pages

There are some pics of one of Paraprops kits that was built into a mud motor (John O'Neal I believe) While the unit cost for the kit is real low, the shipping costs more than tripled the total outlay I recall.

I also contacted another Thai vendor and the same story - cheap kit and very expensive shipping. I don't understand this as I ship many items worldwide on a daily basis. If we could get a group to gether to each purchase a kit, shipping would be nothing when split.

Mark

 

Ripped Off

Hey ripped off!

I saw that you had made a couple of mud motors back on page 28. How fast did your 2.5hp run and weight and what size prop/type did you run on it?

 

tryin something a bit different

hiya all, been enjoying the lightweight boating thing for a bit but batteries are too hard to charge in the wild and these motors use little juice so am trying a weed eater conversion. thought i would start cheap and get the cheapest new weed eater to try out and see what happens $100. what happens is, all goes great till you put the prop into the water, and then the proverbial stall, you can try and try again and all you get is stall. issues were not enough power in the 28cc motor, the high rpm was way to much for the trolling motor prop. waste of money but have a few decent parts to use, tubes, flexi shaft etc.

so i see gearing is the answer and i see i can get a few reduction miter gears for about $100AU plus shipping, yeah right :/, so i head down to the dump instead to see wats there, a bunch of junk indeed, and i grab a 23cc redmax reciprocator for $10 cause it has a strong gear thing at the end, which turned out to be useless for a boat but the rest is awesome, while only 23cc the thing still starts and runs for hours great, has 7.5:1 gear reduction AND a clutch. went the next day and found 2 more weed eaters for another $10, one was an almost complete redmax reciprocator so also have a full parts set as well now and the other has a 45 degree gearbox to save having to bend the shaft too much, will use flexi for the other 45 degrees and have a lightweight 23cc outboard now, tests will happen on the weekend, for now just cleaning the gears etc and sealing stuff best i can

for propellors am using jarvis marine watersnake props because i had some already and luckily they are an anti clockwise prop which was required by the redmax. got a 9inch prop today because at approx 1000rpm max the small prop is spinning slower than with the smallest trolling motor, so am hoping the larger prop will run nice at about 800rpm or so from the 7.5:1 gearing in the reciprocator thingo.

btw am using this setup on a 8 foot sevylor fishhunter inflatable so the boat weighs stuff all and with lots of gear and me maybe about 150lb, since i have to carry it all around waterfalls and log jams am trying to keep boat/motor/fuel/tools to a one person single portage, ignoring the rest of the camping gear/food which requires separate trips. this was possible with electric but 2 x 7ah batteries only last so long.

my questions for now i guess are has anyone trying which such a hich gear ratio on a tiny motor? 7.5:1 with a 23cc brush cutting reciprocator. would a 25cm 2 blade prop with low pitch be unreasonable for a motor like this with a max rpm of about 1000 rpm?

 

One concern

I would be leary of the flexi shaft being able to handle the stress. I have nothing to base this on personally but do know of others who have tried the flexible shafts and had them break after a few hours running. The heat generated was too much and the plastic shaft couldn't handle the load and snapped. Have read this more than once.

You will have to let us know how that small motor with a big gear reducer works out.

Mark

 

impressed with tests

took the motor down to the river and tested by holding the shaft against a log, even at low rpm was barely able to force the motor away from log, has great power, no stalling, clutch engages same as out of water and motor did not stop at any time. drive shaft is solid, don't think i will need a bent drive shaft now if i make the bottom holder on the bracket push the prop away from the boat a little more. need to make a collar to adjust motor depth and then ready for proper test.

the key to the success seems to be in the gearing for sure. the main gearbox just after the clutch is about 8:1 reduction and then another 1.25:1 reduction at the 45 degree gearhead behind the prop giving almost 10:1 reduction, enabling the larger prop to be used it seems. will try get some video of next tests, thanks to all the info found in this thread it just might work.

 

I am in aus but what is a redmax reciprocator ?? Whats it used for that needs a 7.5 gearbox ?

 

redmax

its an edger i guess, has 2 big round blades that go back and forth against each other rather than round and round, thats why i had to replace the head

youtube video http://www.youtube.com/watch?v=bDG6tMsO6AU
specs on redmax stuff http://mticanada.ca/pdf/RedMaxSpecModeles100310EN.pdf , shows the gear ratios etc, mine is similar to the SGCZ2401/2450
exploded diagrams http://weborder.husqvarna.com/order_static/doc/ZIUS/ZIUS2008/ZIUS2008-SGCZ2401S.pdf

is made by komatsu and seems to have nice japanese engineering compared to the el cheapo i first tryed with. they appear to cost about $400 originally but i got 2 for $15 at the dump . go check out your local lawn mower repair center or dump, i reckon this is a real gem and recommend it, is too late to go to river now but will try real test in morning if weather holds off. the next thing to tackle is the noise, what are the best options? can try a double muffler as the output from current one is a nice round tube so easy to attach to, or is adding a pipe to end of muffler into the water the best idea?

added the cost so far on current build including boat