Mini Air Boat Question/Info needed

[Rollbar]

Awesome, thanks. Yes I called Papajack and he is a wealth of knowledge. I would like to see your snowmobile engine and your set up.

Thanks again,
Jim

P.S. How much is shipping for a Snowmobile engine form Alaska-LoL

[Bart]

I haven't looked into the shipping, I have a couple of sleds that I am almost ready to part out. with the new drive belt systems that Polaris has built (http://www.snowtechmagazine.com/pola...mk-belt-drive/) this setup is handling sleds with more than 180 HP.

I have 2 that would be good candidates, stock 600 cc motor that puts out 120 HP. and a modified 600 cc that is 140+ HP. but with that much horse power, but these motors don't have the provision bolt mounting holes for bolting on a gear box.
I just have to many toys and not enough time, and way to many dreams. then I would really need a bigger boat, a bigger yard, and a lot bigger shed, to store these in during the winter, and I think my wife would be giving them away, while I am at work, just so she would have a place for the flower beds.

[Rollbar]

Cool. I have never seen a snow mobile motor/drive system.
I did not know they can produce such H.P. power.
Thanks,
P.S. I'll send your wife my address and if she wants to toss anything then she will know where to send it-LoL

[Bart]

back in the 70's, the rule of thumb was, you would work on you sled for 10 hours and drive it for 10 minutes, now you have the trail and utility models, that are pretty maintenance free, as long as you keep oil and gas in them, then you have the high performance ones. that the weak link is the pistons, and it seems like somewhere between 1500 and 2000 riding miles, it is wise to replace them, but like this last winter, I have had more than a couple of friends lose their motors due to bad gas, but having a way to get to top of the mountains. and having a look around. to realize what a wonderful place we live.
but sometimes the ride up to the top. or back down can be a little hair raising, to say the least.

[Papee]

back in the 70's, the rule of thumb was, you would work on you sled for 10 hours and drive it for 10 minutes, now you have the trail and utility models, that are pretty maintenance free, as long as you keep oil and gas in them, then you have the high performance ones. that the weak link is the pistons, and it seems like somewhere between 1500 and 2000 riding miles, it is wise to replace them, but like this last winter, I have had more than a couple of friends lose their motors due to bad gas, but having a way to get to top of the mountains. and having a look around. to realize what a wonderful place we live.
but sometimes the ride up to the top. or back down can be a little hair raising, to say the least.

This is why I don't run the two strokes, well that and the rpms. I remember times pulling the sled on the trailer after working on it for hours, then traveling a couple hours to the trails only to have the sled not even start to get it off the trailer.

The 084 isn't a real powerful engine and because of the way the bottom end is designed they don't do well with power modifications. I was looking for something reliable after running a modified 18 hp Briggs for a few years. I think I've found it in the 084. It had a bad cyl on it when I got it. I ran it for a while like that, it would smoke and foul a plug after a long pull. I just replaced the head, piston, and rings at that time. The magneto also quit early on. After that the only othe problem I've had was a helicoil blowing out after a backfire caused by carb icing.

Being retired/disabled my build has always been on the very low budget plan. I've had many hours of trouble free fishing. I don't have a speed demon or hill burner but it will do a steady 25-27 mph with a top speed of 30. Minis do have a limit, making a smaller engine go faster and haul more weight can get expensive. When that happens its best to move on to a full sized build.

[Rollbar]

Well I talked to the original owner of the Rotax and he said the motor was rebuilt by Lockheed in Sebring, Florida

Now to revisit the person who has it and see if she will turn over.

[Bart]

sounds like it might make some noise, where it has been sitting for a while, use fresh gas, if gas has been sitting in the carbs, you may have lots of old varnish in them. also.
it appears that it should have oil injection, where i see an oil bottle on the top, where the gentle man had drove it around the yard, it sounds like the the oil line was bled. but verify that there is no air bubbles in the line, usually there is an bleed screw on the oil pump housing you open up, which lets any air trapped in the line or housing get out.( kind of like getting the air out of a brake line on your car,) except you let gravity do the work. there is nothing to pump.
where the owner was driving it around the yard, this (the oil) should be good, but it never hurts to double check.

i cant agree with Papee more about the reliability of the 2-stroke motors. i have fun with them, but i do work on them a lot, a good day of riding is when all the sleds get back to the trailer on their own power.

this might have been why i have been dragging my feet with the 2 stroke option for the past 5 years,

but i think most of us are in this, trying to build an reliable toy, on an limited budget, with the materials that are at hand, at the time.
most of the knowledge i have on them is with polaris motors, but i have had a couple of skidoo sleds in the past, (it is kind of like a ford guy explaining to someone what to look for on a dodge.)
the main concept is the same, but there are a few small differences.
if you do decide to go with it, the motors are simple, but there is a leaning curve, of what to watch /look out for while operating it. most of the problems people have with the newer 2 stokes is the gas, and loosing cylinders due to detonation. (most of the manufactures have gone to EFI) this has taken many of the motor problems away, except when they are not mapped correctly.

from what i read. you are in a part of the country, where the temp does change so much at least that is what we are told. and with an air boat your elevation shouldnt change unless you really go traveling.

with the carburated 2-stoke motors, elevation and temperature changes can raise havic, you are always needing to change the jetting, to compensate.for it. i have had a few friends argue, both make their different adjustments, (because the manufacture doesn't know anything.) all i can say is that their motor ran real good for a little bit. and then we towed them home.

there is one product that i have used that does work with the 2-stroke motors that helps with the jetting, is the holtzman tempaflow. (http://www.holtzmaneng.com/carburetion-products)
if i do end up using the Cuyuna motor, i will be installing one of these on it. i can see myself operating an airboat in temperatures ranging from 80 in the summer to -5 in the winter. that is a lot of jetting changes,
any way, don't mean to be long winded, but have fun,
and if nothing else, that is a heck of a deal for what he is asking for, and i would have a hard time passing it up.

[Rollbar]

Thanks for the info, the gentleman told me they mix their oil because they didn't trust the oil injection when in the air so it sounds like the internals would be fine.
Time will tell and I'll be talking to him.

[fresh water hunter]

do a compression test it will tell you a lot on the engine leaking seals are a 2 stroke enemy how big is the prop i am running a 68 in. on my 70 hp yamaha and yes mix your oil we raced them 250 miles on half mile oval and hold up but do need be maintained properly thats why i am going to the 4a084

[Rollbar]

do a compression test it will tell you a lot on the engine leaking seals are a 2 stroke enemy how big is the prop i am running a 68 in. on my 70 hp yamaha and yes mix your oil we raced them 250 miles on half mile oval and hold up but do need be maintained properly thats why i am going to the 4a084

I'll have to measure the prop/MFG.

[Rollbar]

Question, if one was wanting to run a 4 bladed prop for this engine, where would one purchase said prop seeing it is an ultra-light engine.

Also, will a 4 blade give the motor more snap out of the hole, or what would be recommended IF one was not going to run the 3 blade prop after a while/after testing etc.

Personally, I would be looking for more torque than top speed but I'm not sure how that works. To me (being new/knowing nothing I have been reading whereas prop speed has been discussed around 2700-3k rpm and one thing I do not understand, if most props are to spin at those rpms, then why do some need so much power? Is it the torque they are after, because rpm is rpm. Or is it the pitch and the power to turn such a prop thus gaining speed/mph. Hope I made since, just not computing in my brain-rpm/prop speed etc.
Thanks,

[Bart]

the link below, might have some information that could give you some answers about the 3 blade prop compared to the 4 blade prop

http://www.competitionaircraft.com/specifications.html

[Rollbar]

the link below, might have some information that could give you some answers about the 3 blade prop compared to the 4 blade prop

http://www.competitionaircraft.com/specifications.html

Ok thanks, I'll check it out.

P.S. The wife is getting the bug REAL bad. She just left to go buy me a airboat magazine and she was just on Craig's List and found a caddy engine w/70K on it. Crazy woman.

[fresh water hunter]

check out airboatpros chucks ecotec builds he did a 300 hp all aluminum 4 cylinder turbo engine on a little boat sweet amount of blades depend on length and hp tq you have to turn them plus pitch fist you have to get a motor and weather direct drive or redrive that will give you a prop size prop legnth will tell you how wide the top of your hull needs to be

[Papee]

I agree, the direction you are going the ecotech setup would be a good fit. You wouldn't really need the turbo if you wanted to save some cash.

[Rollbar]

OK thanks for the info etc, I'll google it/chuck/ecotec builds.

Thanks again,
Jim

[Rollbar]

check out airboatpros chucks ecotec builds he did a 300 hp all aluminum 4 cylinder turbo engine on a little boat sweet amount of blades depend on length and hp tq you have to turn them plus pitch fist you have to get a motor and weather direct drive or redrive that will give you a prop size prop legnth will tell you how wide the top of your hull needs to be

Very Nice !!!!!! HP/Torque, but, it's computer driven motor and I'm looking at old school/easier to fix when stranded. Don't have to mess w/PC's, CPS/TPS etc, so I'm thinking a regular motor if the Rotax doesn't work out.
Great info though-Thank you again, Jim

[Rollbar]

Question(s) on the 4a084.

1. On the 4a084 engine that is a 20HP, can it be bumped up to a higher HP? Or should a reduction drive be used/work better since it is 20HP? If so, what would be gained by using a reduction drive with the 084 engine (see pics below from Duane)?
2. Would the 4a084 push a 12'x7' Hard Chime well with two people (400lbs + fuel + boat weight) or should I build smaller (10'/11'x6'6" Hard Chime)?
3. When running a Mini (12'x7' hard chime or 10'/11'x6'6" depending on responses), and having a two person in-line seating arraignment, is it better to have the driver in the front seat? My thinking is yes, and my thought is if I go out by myself it will plane faster but what do I know (I originally wanted to sit in the back and wife up front and have her lower in the boat etc,,,).





Thanks,
Jim

P.S. I know I asked some of these questions, but that was in consideration in using a Rotax 65hp engine. I'm back to the drawing board.

[Corky]

The military rating was a little different than a normal rating{high altitude,worst case senario}..At sea level its closer to 40-45 hp...I'm a hotrodder through and through but the 084 does'nt appear to take radical mods too well...In our application some mods will make the already marginal heat dissipation go over the top and run hotter than you'd want it to...Actually ,running a redrive where the RPMs are sustained up close to the limit seems to make the engine run hotter than a direct drive from the info gathered on this site...

Placing the weight is'nt as you'd expect in an airboat..Too much weight up front actually hinders performance and easy planing ability...General rule is the boat should balance out at close to 3/4 the distance to the transom...Example, a 15ft boat would balance out at the 5ft mark forward of the transom...Keep in mind this is a general guideline...Length and shape of the hull as well as engine HP all affect the balancing...Only way to get it dead on is trial and error after the build is complete...IMO for a mini you want the seating inline a side-by-side seating arrangment will block too much air...My old mini had the operator's seat up front with a steering wheel for years...It never got on plane until I moved the seat back to the guidelines I've posted...

[Rollbar]

Thank you very much Corky.

I found this on the net and some good info from Canada.

These engines produce 45hp and will spin a 54"x24 - 58"x28 prop direct drive producing around 200 - 210 pounds trust at about 3200prm static stripped of all the un-needed stuff.
They do not need any thrust bearing modification since the center bearing is a thrust bearing. They weigh about 125lbs stripped.

I am putting a redrive on mine with a 68" Ivo ground adjustable prop. It should produce around 240 - 250 pounds trust static. I know a guy who put a 72" 3 blade Ivo and got 260 pounds thrust, but at 4200rpm.
These engines are made to run at 3600rpm constant in the generators they were used on. 4000rpm for a few minutes for talk off should be no problem. They are very reliable.

My wish is these great little engines would put out 80hp reliably, however the heads limit modifcations to a minimum because they cannot disapate heat enough for radical modifications.
Shaving the heads 10 thousand is pretty much max. 36mm carb, dual carbs or EFI and exhaust is about it for mods. I will using an a recommended SU HS4 carb because it is a constant velocity carb which adjusts mixture with altitude.

I was reading one forum where I guy tested several mods with no sugnificant gains. He noted the best performance was with the stock intake.