Thai Longtail/mudmotor With 6hp Lifan/honda

[pistnbroke]

Been asked to let you know how the 6.5 Lifan went so here are the photos and some constructuon details. The tail piece has a taper roller bearing which carries the 12mm stainless drive shaft. Propeller fitting is pin drive for a suzuki prop I had ( 8x 7.5) 14mm bore ..since sleeved up to 17mm to take a Yamah prop from a 20 hp Yamaha ( got 3 props on ebay for $50) this prop is 9 x 10 ish and the engine works hard at 3600 to drive it ..but it stirs the pool up real good !!! shaft tube is 25mm gal steel with ball bearing at engine end and bronze bush in centre . Lubrication is 100 ml of auto transmission fluid . engine plate is 6mm steel plate and chain adjustment by washers under the engine ( only 1 needed )

It has a 2.11 : 1 chain drive so I can use a right hand prop . there is a go cart clutch ( max torque) which comes in at 2200. I am not too happly with this as it means rev range is only 2500- 3600 and if you get into regulated waters at 6 knots then your prop at 2500 needs to give you 6 knots ..hence not much top end ...so am thinking of disableing it so idle will be 6 knots .

Up down rotation is with two bits of box interlocked and shapes to give about 15 deg down. may beef this up and put on adjustable stop...

I have yet to finish the chain guard and throttle linkage as well as moving the electric start to the "front "..hope you like it and have left space below for more pictures....

[pistnbroke]

Here are the photos of the articulation joint ..the two U sections are the same size ..bolt stops sideways movement

[John O`Neal]

Great job. Well done . What is the rpm limit for the Lifan motor ?

[pistnbroke]

Idle seems to be about 1650 and governed max 4000 .research into go kart sites indicates that you can go to 6500 rpm with the standard bits and 8500 with a stronger con rod and valve springs ..HP to about 10 seem possible with new carb/head/rod /camshaft ..thanks for your interest

[ben2go]

Sweet set up.I was looking at doing one with a 2.5 I posted on the other thread.What is the over all length?I want one for my 10 foot jon boat.My outboard hangs to low.

[pistnbroke]

from the piviot point to the prop is 64 inches...remember if you drive straight off he crankshaft you will need a left Hand Prop and the smaller the HP the more difficult these seem to be to get hold of (cheap) You wont build it unless you can weld and it will be difficult to do the bearings without a lathe but not impossible..I have put some notes on where to get left had props in the US on the weedeater post ..thanks for your interest

[TerryKing]

... You wont build it unless you can weld and it will be difficult to do the bearings without a lathe but not impossible..
Many thanks for putting your work out for us to learn from.

Can you show a little more detail on the thrust bearing and it's mounting?

Also, is there a 'seal' at the water end, or just the bronze bushing??

THANKS!

[pistnbroke]

there should be a picture below ..

Drive shaft is 12 mm stainless steel brazed and roll pinned into the prop carrier
Prop carrier is made from a length of 16 mm stainless bar the idea being that the factory finish 16mm dia will ride inside the oil seal which is 16 x35mm
Thrust bearing is a taper roller 14 x35mm and the thrust is taken on the step down from 16mm to 14mm
Propeller mounting was to suite a Suzuki prop being 14mm bore and with a cross pin drive.
Securing nut is attached to an 8mm SS bolt brazed into an 8mm hole in the end of the shaft.
Engine end of shaft is supported on a 12x35mm sealed ball bearing race and half way down the shaft is a bronze bush 50mm long held with two grub screws
Lubrication is with 100ml of Auto Transmission Fluid and there is a filler hole/plug above the bush
The mounting for the bearings was from a lump of 40mm dia steel bar bored to suit bearings/seal and welded to the pipe ( 25mm galvanised )
Mounting the 26t chain gear to the end of the drive shaft is tricky...make up a boss ..weld to gear THEN with gear held in outside jaws drill the central hole..even though its a chain drive it mist be dead on. Chain is 36 pitch to match the MaxTorque go kart clutch.
If I was doing it again I would put an oil seal at the engine end of the shaft as there is some loss if its not prop down in storage .
If I was going to drive stright off the engine shaft I would not use the universal joint but a straight coupling.Mount a 1/4inch steel plate to the 4 bolts that surrund the output shaft from the engine and then 4 triangular plates welded between that plate and your drive tube .additional support from below.
If you use the chain drive apart from the right hand prop it is much easier to mount he drive tube under he engine rather than try to support it in front of the crankshaft .You can just weld the tube to the plate on which the engine sits ...chain adjustment by washers under the engine mounting bolts .
Not sure if the clutch is a good idea or neccessary as it limits the rev range from clutch engage( 2200 rpm) to 4000rpm . without the clutch you have range from idle to 4000 ..just start out the water and drop it in ...
Balance should be a positive prop down.
Make sure the engine cuts out if you fall overboard.

[mudman]

Neat set up. I like the idea of having a thrust bearing. In the swamps here we just use a shaft directly coupled to the engine. Put a shaft tube with a cutlass and you're good to go. Very simple and effective, but the thrust runs through the engine. Haven't had problems with it yet. Trick is to mount the engine on the boat so that it is balanced.

We figured out that with a shorter shaft and a mud prop with extra cup you can run the unit as a surface drive. We can get more speed and get through even more stuff. Run right over mud flats with mud flying. The engine has to mounted lower on the transom though. Thet work great in flat back pirogues. I think that the cost for mine to build was about $1K US. Worth their weight in gold though if you ask me.

Very nice set up.

[newinertia]

this is one of metalboatkits.com 12 ft. skiff, scaled to 7'6'' .125 5052h32
trans is a comet industries torque a verter.

[TerryKing]

there should be a picture below ...
Thanks! For showing us those details. Always something to learn from someone who is figuring stuff out! When I get home this Summer I'll get a motor on my old 1938 South Bend lathe and see what I can do...

[notsofast]

What boat did you mount this on? How fast did it go?

[pistnbroke]

its all down to if you can get your hull on the plane ....this usually happens at about 15 kts.........then you can run on to 20 kts ...if it wont plane you are probably stuck at about 12 kts.
Of course you need the right pitch prop ..mine is a 10 x10 but remember its geared down 2.11 to 1

[notsofast]

Thanks for the info Pistnbroke. I'll be mounting my engine on a home-made surfboard, flat bottom, so planing should be easy.

[notsofast]

Hello Pistnbroke,

I'm doing 17.3kts (GPS) on the surfboard at 5,000rpm WOT, 2-bladed prop 6.75" x 4.7" (crude measurement, crude prop). Engine is 200cc honda clone, kenbo brand rated at 6.5Hp @3,600rpm. Prop is slightly aerated, about 1/2" is out of the water.

The home-made "surfboard" is very flat, no rocker, 12-ft long 3-ft wide 4" thick, plywood & epoxy. No "hump" going from displacement to planing.

Assuming I can get whatever prop I need, will there be any substantial gains if I go for 1:2 gear reduction using the same engine? I figured efficiency will be higher with slower/bigger props but by how much? The propshaft will be turning much slower too, if there's any gain in that. The shaft simply goes through a greased brass tube, no bearings. Thrust is taken up by the engine. Propshaft angle is 14-deg.

Sorry, dunno where else to post my question above.

Thanks,
notsofast

[jonr]

Nice work, thanks for the pictures.

Is there any concern about the engine running tilted? - I assume it is splash lubricated.

[pistnbroke]

Not so fast ......well thats basically 20 mph which is what I predicted.If you gear it down you will not increase power ( which drives the boat ) but torque so you can drive a higher pitch prop BUT SLOWER so no gain ...

Your biggest problem is that greased shaft ...6 ft of greased bearing ..that consumes a lot of power and riding the thrust on the motor is not a good idea ....other gains by increasing engine rpm ..look at johns modded engine on the other thread ..weedeater conversion

[muddin redneck]

so pistn i was just reading the new posts on here and you say not to use grease. i am in the process of building a go devil type mud motor with a 24hp honda and i am at the point of the project where i decide to put grease zerts or an oil fill plug so what do you think i shoud use? the store bought go devil has a grease zert and a pressurized grease can on it and the tube is filled with marine grease. i was first thinking about using grease i thought it might help keep out any water because its thicker and water wont mix with it, i know it wont mix with the oil either but i could get water in the oil though. any input would be greatly appreciated. i will be posting some pics soon i hope.

[pistnbroke]

think you missed the point ...he said he had a tube with no bearings just the drive shaft running in grease inside the tube ...thats a 6 ft long bearing ..lots of energy to churn the grease ....if you had say 3 bearings (ends and middle ) clearly a lot less area and grease to churn

You need a drive shaft say 1/4 inch less than the inside of the tube and push in a T bearing at the prop end with plane bearings centre and top ..Nylon Bronze Brass and grease it before and after use through a grease nipple. that is if you have not got the engineering machinery to handle sealed ball or taper roller bearings . you need a slideing or adjustable link to the motor so its bearing is not used as a thrust bearing ...splines would be best

[notsofast]

Thanks pistnbroke, although that leaves me scratching my head...... :confused:

Why do 99% of all outboards always use gear reduction? And marine transmissions also have reduction? Same with stern drives I think, not sure. Maybe there's some gain in going for reduction? Not to contradict you, just trying to help my understanding that's all.

Yes I do understand what you're saying about the grease. Will slower shaft rotation help with the drag?


--------------------------------

[pistnbroke]

outboard engine runs at 6500 not the 3600 of the lifan so they reduce the rpm as the prop is more efficient....comercial tanker about 100 rpm ..I have a real briggs and stratton outboard and they do a 1.53 reduction on the 3600 for the prop ......model boat engine 20,000 straight off the crank though some do use a reduction gear ...

[muddin redneck]

sorry for the confusion pistn, i was not talking about notsofast's setup i was wanting your opion on a home built mudmotor that i am building it has a tapered roller bearing in the shaft on the prop end for thrust load, then there are 2 brass bushings spaced out in the middle of the tube for shaft alignment, and then there is a greasable flange bearing at the top of the tube for side load. the flange bearing is not inside the tube though it has its own bracket that holds it in place. tube is totally sealed at both ends. i am wanting to know if you think i should use a marine type grease or an outboard lower unit type oil. i am going to vent the tube at the upper end for oil or grease expansion so i dont blow out the seals. does it all sound feasible?
thanks, muddin

[pistnbroke]

best thin oil for bearings would be automatic transmission fluid ..I have that in mine

[thudpucker]

I sure enjoy seeing other guys ideas in photos. PB's will be a big seller among the Lilly pad fishermen.

PB, did you figger that all out with a sliderule before you made the first piece, or did you start making pieces and make them fit later? :)

[pistnbroke]

got a lathe a welder and a brain ..just went to see what bearings I could get etc its not a big engineering problem ..bit crude really BUT IT WORKS !!

[Frosty]

sorry for the confusion pistn, i was not talking about notsofast's setup i was wanting your opion on a home built mudmotor that i am building it has a tapered roller bearing in the shaft on the prop end for thrust load, then there are 2 brass bushings spaced out in the middle of the tube for shaft alignment, and then there is a greasable flange bearing at the top of the tube for side load. the flange bearing is not inside the tube though it has its own bracket that holds it in place. tube is totally sealed at both ends. i am wanting to know if you think i should use a marine type grease or an outboard lower unit type oil. i am going to vent the tube at the upper end for oil or grease expansion so i dont blow out the seals. does it all sound feasible?
thanks, muddin

Why not put your hole at the top like you said and put an oil resoviour on the hole to feed the tube. Something like a brake fluid bottle.

It would also be a kind of tell tale that all was well, if level changed something was wrong.

[notsofast]

Thanks Pistnbroke, it makes sense now. :)

------------------------------

[mcollins07]

Here are the photos of the articulation joint ..the two U sections are the same size ..bolt stops sideways movement


Very nice job Pistnbroke.

What is the diameter of this rod or pin? is this plenty strong? and width of U sections?

~ Michael

[pistnbroke]

my us section is a bit narrow ...I would use 2 or 3 inch. the pin is 8mm so go for 1/2 inch ....my main modification would be to set the shaft under the centre of gravity of the engine so the chain would be a little ofset rather than up and down

[Ryan6x6]

hi I'm knew to this forum i want to build a long tail for a 14 foot john. i was looking at the Greyhound engines at harbor freight.com the have a 2 1/2 96cc four stroke for under $100 and a 6.5 for $160. dose anyone have any experience with with these engines? any advice would be helpful thanks.

[pistnbroke]

Well if its a 14 ft boat you can aford the extra weight of the 6,5 and you will have more power as well as finding it easier to select a propeller ..if you drive straight off the shaft you need a left hand prop !!!
Have a look at weedeater conversion particularly john tod postings and anything with photos

[Ed-H]

PB, did you have to machine a taper in drive tube to accept that tapered thrust bearing? I've only seen them used on car wheels, and they ride on tapered races. Also, is the entire bearing inside the drive tubing? I'm having a hard time envisioning how you used it at the prop end of the unit.

[Ed-H]

How thick is the wall of the 25mm galv. pipe?

[Ryan6x6]

thanks for the advice the 6.5 greyhound engines also have push button starts as well. would be nice not to have to worry about pull starting the engine next fall.

[pistnbroke]

study the diagram I posted earlier and you can get taper roller bearing s in a whole range of sizes inc the outer thrust ......yes its all enclosed behind the oil seal so you can lubricate down the shaft from the engine end

if I give you good information give me feedback if you dont like it dont

[Ed-H]

PB, I did study the diag. and pretty much follow everything you have there. Since the drive tube, was not included in the diag., it appears you MUST have had to machined a taper on the inside of the tube for the bearing to run on. Am I correct in this deduction? thanks in advance.

[John O`Neal]

i was looking at the Greyhound engines at harbor freight.com the have a 2 1/2 96cc four stroke for under $100 and a 6.5 for $160. dose anyone have any experience with with these eng

Ryan; I have both of those engines on my Thai longtails. They are very dependable an will give you good service for the money. I have a buddy in North Carolina who just bought a 6.5 hp model for $ 90 on sale at Harbor Freight. I paid $ 99 for mine in Kansas City. Those engines go on sale every couple of months so ask the store manager when the next sale will be. I would strongly suggest you go with the 6.5 hp model for a 14 ft. Jon boat. I own both size engines, on Thai longtails, so go with the 6.5 you will love the extra power. Look at the weedeater conversion thread on this forum and you will see both engines shown there on longtails. Good luck with your build. P.S. Get the electric start model if available.

[Ryan6x6]

thanks for advice John o Neal I'm going to go with the 6.5 with the electric start. would galv. pipe be better than aluminum for the drive tube? i have been looking at Turn4Funs plans and think i can modify it to work with 3/4 inch drive shaft instead of 3/8. I'm going to start this project this weekend want to give myself plenty of time before next duck hunt.

[John O`Neal]

would galv. pipe be better than aluminum for the drive tube?
Ryan; I have three longtails one wih an aluminum tube(brushcutter conversion) and two with galvanized steel tubes (Thai manufactured) . They work equally well. I know that the tubes are also being manufactured from stainless. This one may boil down to personal preference. But in an attempt to answer your question. If it is not going to see extensive use in saltwater I would go with aluminum, simply because it`s lighter. Good luck with your build.

[Ryan6x6]

Thanks John I'm in Utah we have both fresh water and salt water depending on were i hunt becouse of the great salt lake, sounds like galvanized is the way to go.What would the best size tube be for 3/4" drive shaft is the 1"x .125 wall thick tube still going to work or do i need to buy a better size tube most of the info on the thread is for the smaller brush cutter convertions? thanks

[pistnbroke]

3/4 drive shaft is far too big and heavy enough for a 200 hp outboard ..keep the weight down go for 3/8.....the 3/4 is 4 times as heavy !!!!!

[Ryan6x6]

thanks was looking at John o Neals pic of 6.5 with u-joint and it looked like 3/4x3/4 u-joint with 3/4 drive shaft. who sells 3/4x3/8 u-joints McMaster-carr?

[pistnbroke]

you make up a sleeve 3/4 outside and 3/8 inside .....anyway john has gone away from using a u joint and has a stright link and tilts the motor ...just lilt and top up the highest oil filler hole

[Ryan6x6]

thanks for the information pistnbroke it helps

[TerryKing]

Hi Everyone, and thanks for such a great collaborative project...

Has anyone used one of the 'Greyhound" AKA Chinese OHV engines from Harbor Freight? They are from 6.5 to 13 HP..

Examples:
http://www.harborfreight.com/cpi/ctaf/Category.taf?f=bylogo&logourl=greyhound_logo.jpg&brand=Greyhound

(Others below)

I know I can get these delivered to my backwoods in Vermont...

Thanks!

[pistnbroke]

they are identical to the honda /lifan /etc /etc ....so no problem lots of posts on them recently on this and weedeater conversion posts....

[Ed-H]

Of course you need the right pitch prop ..mine is a 10 x10 but remember its geared down 2.11 to 1

PB, can I ask your opinion on using a 7x9 prop on a 4hp 4 stroker? Could it be run w/o reduction, or do you think it would be better with? The boat is a 14 sneak/layout design.

[pistnbroke]

too much maybe start with or 7 x4 and bend the blades if neccessary ..for direct drive

[Ed-H]

Do you think it would work if I were to gear it down like you did?

[pistnbroke]

depends if its a left or right hand prop ..if it right hand I think my design is good because it gives rigidity to the system without excess weight ...you have to make sure the link between the motor and shaft cannot bend with a direct drive which takes a lot of angle lron engine to shaft ...you can build my design with U bolts .... simple plate with tube underneath U bolted to a 1/4 inch steeel or ali plate ......you still have the same bearing problems to deal with ...

[siberian]

Hey Notsofast, I'm looking to put a mudd motor on my surfboard. We need to talk. How much does yours weigh?
I'm got a Starboard Go 180 liter displacement. It's 8' X 3'.
Could you please post some pix.
Thanks

[siberian]

Hey Notsofast, I'm looking to put a mudd motor on my surfboard. We need to talk. How much does yours weigh?
I'm got a Starboard Go 180 liter displacement. It's 8' X 3'.
Could you please post some pix.
Thanks

[notsofast]

Hi Siberian, I originally tried a surfboard (40lbs) with a 3Hp outboard (35lbs) but couldn't get it up on plane. The surfboard was 12-ft long by 2-ft wide. This idea was junked.

Then I tried a 200cc Honda clone (new carb, advanced the ignition timing, high comp cyl head) with a 3-ft wide by 12-ft long wooden "surfboard". This worked quite well and can do 25mph consistently, as measured with a gps. Took me several trials with different props to get to that speed. Some pix here -----> http://www.pinoyboats.org/forum/viewtopic.php?t=1289&postdays=0&postorder=asc&start=120

180 liter? Maybe 180cc?

Good luck with your build!

[notsofast]

Here's a couple of props that were tried. Fastest speed was attained with the 2-blade, hi-rake prop.

[rmenasco]

pistnbroke, could you please show some photos of what your design looks like under the motor? I am interested in your design.

[muddin redneck]

notsofast, where did you buy your props for your motor?
thanks,
muddin

[pistnbroke]

just too bits of ange about 3/4 x 3/4 to make the welding easy ..you could use U bolts if you leave space under the engine but main mistake I made was not to get the centre of gravity of the engine over the shaft ,,,,so mine is a bit lob sided.....you need the shaft nearer to the cylinder side for balance

[rmenasco]

pistnbroke,

Thanks for the photo of underneath the engine that was really helpful! I am a newbie at this so I have a few more questions for you. I just finished building a "hybrid" duck boat from www.hybridduckboats.com . I have attached a photo of the boat below. Do you think I would need the same 10x10 prop if I used a 2.5hp? Or should I go with another prop size? Also, what is the set up on the bearing closest to the sprocket?

Thanks in advance!

http://hphotos-snc3.fbcdn.net/hs539.snc3/30571_592425554295_201400849_34645850_5512997_n.jpg

[pistnbroke]

the size of the prop depends on the engine power so if yours is 2.5 and mine is 6.5 then you are going to need to reduce the pitch in proportion ....probably something like a 8in x 4 pitch.......similarly you may get a bout 8 kts

the bearing drawings are on an earlier post but its a sealed ball bearing 8mm x30 or similar ( my shaft was 8mm )

[rmenasco]

Thanks for the info! I may just go with the 6.5 since it has electric start and it only weighs 8 more lbs. How fast does urs go? And what size/type of boat do you have it on?

Thanks!

Robert

[pistnbroke]

I have a 5 m 1 m wide rough bottomed canoe you can get about 18 kts

BUT it depends on the pitch of the prop and if you can get up on the plane ..thats usually about 15 kts and all that depends on the weight of the boat ..weight distribution and hull area ...

[Killiant]

Hi, I am new to this site. I saw your post and thought you might be able to help me. I am looking to make a diesel longtail motor for an oyster barge. The engine I have in mind is approx. 50hp. The barge unladen is about 2.5 tons and laden about 9 tons. At the moment I go through about one 70hp petrol outboard every 18 months to 2 years. What I am looking for is advice or drawings (if available) on the shaft and propellor. Would using a gearbox be an option or just a clutch plate for neutral and just a forward gear? Also what would be the best way to couple the engine to a.the gearbox if used or b. if it is just direct drive? I have seen various options on youtube videos such as chain and sprocket, cv joints, and belts and pulleys.

[rmenasco]

Pistn, my boat is only about 2.25m by 1m and it only about 30kg, so my boat should be able to go a good bit faster. So you don't think the 2.5 would be able to get it up on a plane? I just wanna make sure that I make the right motor choice before I commit to something!

[pistnbroke]

if you can take the weight go for the bigger motor /do you have to carry the motor and boat to the launch site ? all to be considered inc shull shape and your weight .....how many burgers does it have tdo carry ? !!!

[rmenasco]

burgers? Never heard of that.... It only needs to hold myself (170lbs) a few dozen duck decoys, shotgun and shells. Maybe 220lbs total.

[pistnbroke]

ie are you a fat bastard ?

Result....

[rmenasco]

lol I wouldn't call myself a fat bastard! About how much did you spend in materials to build yours. You are in Australia right?

[pistnbroke]

bearings .seals tube shaft and the rest was bits out the shop ...about $100

[rmenasco]

guessing you that all the parts from mcmcaster?

[pistnbroke]

sorry dont understand that .....mcmcaster what is that ?

[ben2go]

http://www.mcmaster.com

US hardware supplier that carries unusual and hard to find items.They all so deal in small quantities where most other companies only deal in cases or lots.

[pistnbroke]

looks brilliant ..you could build the whole unit from there bits ...Particularly like the double row chain sprockets ......12 teeth for the engine end but would need an adaptor from the shaft dia down to the sprocket .... get teeth with multiple of 3 then they will go in the lathe ok .....or put the engine on the lathe bed and set it going and turn the shaft down ...thats what they do in Asia !!!!

[notsofast]

notsofast, where did you buy your props for your motor?
thanks,
muddin

Those props are hand-made by a local prop smith here in the Philippines. Stainless steel sheets are shaped by hammer & anvil then welded onto threaded hub (5/8" thread) then polished.

[muddin redneck]

Those props are hand-made by a local prop smith here in the Philippines. Stainless steel sheets are shaped by hammer & anvil then welded onto threaded hub (5/8" thread) then polished.

do you know what it would cost or if it was possible to ship these props to the usa

[notsofast]

Redneck, sent you PM.

[riverrat87]

Hey guys, I'm attempting to follow in yalls footsteps with a 6.75 briggs off of a pressure washer and I'm not sure how to figure out what sprockets I need for the right gear reduction. Any ideas? Thanks in advance.

[thudpucker]

Keep the B&S running at 3600 Rpm.
Now you need to know the prop Pitch, and Diameter.
Then you get the info on the load that will create.
Then Gear the engine to the Prop using percentages.
Then convert the percentages so Sprocket sizes.

[pistnbroke]

anything around 2 to 3 to one seems ok depends what prop you have to hand you could try to match it . .I think my big cog is 28 teeth small one 12 ..if you go much bigger in teeth the large cog gets physically quite big . If you can do a double chain its even better. I think Mc Master Carr have a selection of cogs mail order

You can get b and s with reduction gearbox attached

[riverrat87]

I haven't got a prop yet, should I go with a three blade or two blade

[rmenasco]

Pistnbroke,

I have really been looking around a lot on the internet and I found a company over here in the states that is commercially selling the same thing that you have built for around 1000.00USD

Here is there site....

http://www.scavengerbackwater.com/