redlined_b16a

I'd like to build a pusher set up

I have several engine options but I'll start simple.

I have a very old in great shape Mcculloch 22cc blower motor,recoil in the rear,flywheel as prop side,love this engine because its small and its a simple one fuel line carb,no primer.Alot of compression.I have pulled the case apart and shimmed the crank to help the pusher load.

I have a 10 year old echo 23cc blower engine,runs great,small and built similer to the 22cc.I have already fabbed a mount for the echo,I still need a prop adaptor to get the prop futher away from the engine blocks

I have a 28cc 4stroke,big and heavy
25cc husky chainsaw,very old runs well,small

50cc huskavarna chainsaw,like new engine

My plan so far is to use either the echo 23cc or the McCulloch 22cc,McCulloch seems to have more power.
I bought a 13x7 3 blade pusher prop a few years ago for those engines but when I bench tested the echo with the 13x7 the rpm's didn't seem more than about 6000 rpm's at most.I have no tach,just guessing.

What do you feel the recommended prop size for a 22-23cc should be at for a decent starting point?
How many pounds should the total rig weight for the small engines?

Would lowering the motor close to the hull and using size 25 chain and sprockets with a 1.5:1 reduction or 1.2:1 spin the 13x7 prop at a higher rpm by freeing up a lil more horsepower.
I will also look into a boost bottle as they can add horsepower.
I'll get some pics of my engines.

redlined_b16a

arcdude

welcome redlined_b16a Glad to see someone else out here. Unfortunately I can't offer you a whole lot in the way of advice other than with the motors your planning on using are limited on hp to start off and I wouldn't expect them spin much over 7000 rpm at least to my knowledge. The prop you currently have on may be bit much and if I'm not mistaken the 13x7 sounds about right only in a two blade prop. Adding a boost bottle will only serve to shorten the life of the engine significantly however if you came up with the right combination of engine prop and hull design/weight you shouldn't need the extra boost. As for weight my guess would be in the area of 8 lbs total hull and engine.

As mentioned I have limited experience in this particular area so what I would suggest is to look through the board and find a style of boat with a weedeater or the like and try to contact the person that placed the post, at least you will get first hand knowledge to lead you down the right road.

Cheers,

redlined_b16a

I ran both engines this morning and the echo seemed to really rev high with that 13x7,I played with the fuel settings on it and it really woke her up..So I guess I'll either use the cheesy boggie board method since its the lightest possible way.And experiment with that.Do you think my prop is far enough from the engine?I feel it should be futher but that's the only thing I have for now.Its very fuel efficient too.Im impressed that on a 75cc tank of fuel I ran for about 15minutes and still have more than half that fuel left.

arcdude

I would think as long as your not running the engine too lean and at least an inch between the prop and motor there really shouldn't be any issue. There should be a plate or engraving on the side of the engine with model and so on, if you look it up on the web you should be able to come up with max rpm, carb and other settings that may be helpful in making final decisions on prop and so on.

I know other people have done similar set ups so you should be able to find something in the forums to give you some direction. Good luck on your build.

redlined_b16a

its an echo pb2100,I'll google search again.

arcdude

Here ya go, sounds like the right one. At least I was close on the max rpm being 7400. I'm not sure about the cost of a small tach to figure out what rpm your running and if money is tight and the engine is on a stand and safe to run drop by a local garage they may be willing to tach it for you. I did locate the user's manual but the system won't allow a pdf document, it wasn't hard to find.

redlined_b16a

thankxz for the pdf,I found it as soon as I posted the model number.
If I had to guess its turning out 5000-6000 rpm loaded,pushes a good bit of wind also.I dropped the engine today and broke off the high speed needle but its running fine so I'll worry about it next time it needs adjustments.Next step is a prop adaptor,work on the boogie board.My step son is really excited now.

arcdude

Here is a suggestion and I don't mean to imply you don't know your way around computers so please don't be offended. I did a google search for "weedeater powered airboat" and when google brings up the page you'll see a heading part way down the page entitled Images for weedeater powered airboat and when you click on that it brings up a page of all types of airboats your interested in building. If you right click on an image and open in another tab it brings up the picture and more often than not it states visit the page and if you click on that you'll likely find a whole build of such a boat and possibly all the information you'll require to complete you project. I did see a few boogie board type boats so it may help. Not trying to get rid of you, merely trying to get you the right information you need. Cheers,

arcdude

Stumbled onto this one may be of interest, it's fairly straight forward and not terribly expensive being foam covered in lite plywood, might be worth a look.

http://www.rcgroups.com/forums/showthread.php?t=1756295

redlined_b16a

Im pretty good at google,found loads of them.
Im missing tech info like what angle to set the engine.I see a lot of boogie board puller set ups.

arcdude

My advice is to design the mount so the engine can be shimmed up or down as needed due to the fact you'll be building an unproven boat and you'll likely need to play with engine angle and what not to get it to run decently.

redlined_b16a

Im happy with the engine rpm of this pusher,so If I wanted to switch to a puller what size puller would better suit this lil engine.For a 21cc its a lil powerhouse.
say a 13x 2 blade