building my first airboat

[Duane Scarborough]

Airhead,

It sounds like you have a plan.

I think that wide hull aluminum Jon boats are rare everywhere. That is, unless you buy new, and then you'll pay a premium price.

Seems like those that have a decent used one don't want to let them go.

If you get the right starter-generator they work well on a 4A084. But they are not all the same. Some don't have enough torque to spin a 4A084 over well. They were/are usually used on engines less than half the size of a 4A084.

Besides the torque thing, they don't all turn the same direction. If you plan to mount the starter-generator tucked up under the engine, using the rope start pulley, you'll need a CW starter-generator.

If I'm not mistaken, the Cub Cadet starter-generators are CCW rotation. If so, that may be a little problem. You need to look into that.

I've been told (by those who've done it) that a 4 pole CW starter-generator, with a 2" diameter serpentine pulley on the starter-generator, running a serpentine belt to the almost flat rope start pulley (slighty larger than 6" diameter) works well.

The rope start pulley looks flat, but it is not completely flat. Some say you need to have it machined flat. Some say that it's close enough, and doesn't matter, and some say that you need to have grooves machined in it to match the belt. I'm planning to try the "close enough" approach at first.

Finding a 2" diameter serpentine pulley to fit the starter generator is not tough. I picked up a 6 groove one at the local rebuilder shop for $8.

Good luck,

Duane

Edit: I did a little research, and discovered that some Cub Cadet starter-generators are CW rotation, and some are CCW rotation. Go figure.

[Duane Scarborough]

Airhead,

I just remembered that I'd said that I had a link to a 4A084 engine manual, but I never sent it to you.

Here it is:

http://miniairboatassoc.com/downloads/4A084a.pdf

I think that Papee was the one who originally posted it.

There's a lot of good info there, after you get thru the gov't BS.

In case you haven't ran across it yet, here's another link that may be interesting:

viewtopic.php?f=16&t=294

And then there's this, one of my favorite mini airboat eye candy videos:

http://www.youtube.com/watch?v=sLjw4v9DtMg

That was (I think,) the first test of the 105 minipro hull, which was the prototype before the minipro 116 hull, which I have. The 116 is a foot longer, and a foot wider. I think that was a 35 HP Briggs. Doesn't matter. I love this video.

Duane

[airhead]

Thanks Duane,

I have already downloaded a copy of the TM and you are correct about the b.s.. But i'm very familiar with that crap after spending 28+ years in the national guard and all of it in maint. I also worked full time at an OMS for eight years and actually maintained a lot of these engines, mostly the smaller ones but some of the units had some 10 kw's with the 084. And about the starter; I have a couple of them but have no idea of rotation and poles. I was going to check on that yesterday but went on a chase for a hull which didn't pan out. I am going to try a pulley off an alternator. Maybe it can be modified to fit with a little machine work. Jim

[airhead]

I have a gen/starter that turns the correct way but don't know if it will turn the engine over yet. This one came off a 12 hp B&S. I took the pulley off a junk delco alternator and it fits perfect. I am going to pull the start pulley off and probably machine it flat. Now all this seems too easy, so my concern is will this actually work? I saw one on the experimenter site but never read where it actually cranked the motor. Anyone know?

Jim

[Duane Scarborough]

Airhead,

The pulley I have is an 2" dia alternator pulley. It fit perfectly, but didn't have a keyway. I took care of that in a few minutes in the machine shop at work.

I've seen Ron Paxson start his boat. His works O.K., but could stand to be a little stronger.

They are so many different starter-generators out there that the only way I know for sure to find out if it will work is going to be actually trying it. It it's not up to it, then you start looking for one that will. At least you'll allready have the brackets, etc. done.

Good luck !

Duane

[airhead]

Thanks Duane,
I understand trial & error thats kinda been my life: Learn the hard way. But from now on i would like to try to pass on information that might be helpful. I may have missed the same info since i'm a newby but will try to help other newbys. I had to build a puller to get the rope starter pulley off but when i did i discovered that it is flat across except the radius at the rope end. (Good thing because my laythe will not chuck it up.) I will try the belt without machining the groves but am concerned about how tight the belt has to be. I haven't had one of these start/gens apart but if they just have a bushing on the business end then i see problems. Now for another matter i am concerned about the kickback everyone talks about. With the impulse this should not be a problem if the timing is right. Now don't get p.o.'ed because i don't know. If it is flooded maybe? Airhead need more input.

Airhead be tired now and is signing out. mucho gracious amegos.

[Papee]

I'm on the second year running the 084 on my boat. In that time it's kicked back maybe 4 times and every time it did the prop was off when I tried to start it. This was using the rope pull.

[Duane Scarborough]

Airhead,

My starter/generator appears to have a real bearing on the business end: (sorry about the fuzzy picture, it looked fine on the camera's screen)



They may not all be the same, but I'd assume they would all have real bearings, considering the service they're intended for.

Alternator pulleys do not have keyways. They are held in place only by the clamping force of the nut on the end of the shaft.

My starter/generator was cut for a woodruff key. I had access to broaching tools, so figured I'd be dumb not to broach a keyway in the alternator pulley.
It'd probably work fine without it though.



Here's what it looks like assembled:



From a different angle:



This is a 4 pole / 5 terminal Hitachi starter/generator that can be wired for CW or CCW rotation. I've been told by a friend that has used them on airplanes that it has PLENTY of torque for a 4A084, if you use a 2" dia pulley.

I am planning to hook it up for starter duty only.

"The 4A084 has a perfectly good alternator under the rope start pulley, and it'll put out a solid 12 Amps at 12 volts when used with the right voltage regulator. Aircraft Spruce has a voltage regulator that works well with this arrangment."

That's more advice that came from my 4A084 flying friend.

Enough for now.

Later,

Duane

[airhead]

Great info Duane,
I started to cut me a keway but am going to try with a crush washer on each side. I may have a problem anyway because i think my starter is only a 2 pole. About the charging; i considered the existing alternator but removed it due to added weight. This may be the airplane stuff in me but we have to consider every pound.

Jim


P.S. Can someone help me with posting pictures? Is there any info on the site?

[Duane Scarborough]

Airhead,

That's fine, go ahead and waste a good alternator !

Only kidding. if everyone did things exactly the same, this would be a boring world, wouldn't it.

I think there is something here to help with posting pictures. I'll look for it, and be back.

Duane

[Duane Scarborough]

Airhead,

I didn't find it. I thought that Papee had a "how-to" somewhere.

Well, here's how I do it. (this is not the only way, or maybe not the BEST way, but it works for me)

I have a photobucket album that I post my pictures to. I can add links to that album from here, or most any other furum that I participate in.

Maybe this will help:

http://tutorials.photobucket.com/tutorial_150.html

Duane

[River Rat]

Airhead, The suspense is killin me, man! Hope you figure out the picture thing soon and post up some progress pics on the engine!
... By the way, have you thought about trying to crank the other engine yet? Done anything with it?

[Papee]

Easiest way to post is pic. When you are posting look for the browse button, click it and look for the photo you want to upload on your computer. Then click on add the file then submit as you always do. The photo needs to be 800x600 or smaller to use this feature.

Or, you can register to the gallery at the top of these forum pages. The gallery will resize your photos for you if they are too large to post here then link them using tags. I recommend starting a gallery if you are doing a build then all your photos will be in one place.

[Duane Scarborough]

Airhead,

I said several posts back, that "I'm planning to have mine (prop tip) about 3" above, and 3" forward." (of the transom)

As I was sketching and measuring for my prop cage this past weekend, and thinking back, I realized that I'd told you wrong.

Actually, I'm planning to have my first prop about 3" BELOW and 3" forward of the transom. I had originally built my engine stand for a 60" prop, so that the tip of the prop would be level with the transom. Then I ran across the deal on the 66" prop. That'll put the tip of the GSC adjustable pitch wooden prop BELOW the transom by 3". NOT 3" ABOVE as I stated.

I said it wrong, and wanted to clear it up before I forget. It probably doesn't matter to you, but I wanted to get it straight.

Some of the high HP guys intentionally put thier prop tips very low, so that the hull is "self bailing". That's not my intent. I just screwed up and didn't type what I meant.

Once I get things working, I may go with one of Arrow Prop's wide 3 blade 60" props. They are supposed to be very good performers, and QUIET, which is one of my objectives.

Thanks,

Duane

[Papee]

The higher HP setups don't lose much by having the prop below the transom but with the mini s we want to get everything out of them that we can, this means keeping the prop tips above the transom. As far as the clearance front to back, it is whatever your hull "likes" as far as balancing the hull for weight distribution. My hull is long so I was able to put the engine rearward as far as possible. Depending on the hull length and seating setup you may have to move the engine forward a bit.

Having the boat balanced the best you can get it means a lot when it comes to it's overall performance. I have mine balanced for one person because I go out fishing alone most of the time. I have my battery and fuel tank loose so I can move them rearward when I haul another person to even out the boat. I test mine by "gliding" I get on the gas then let off and see how far I can "glide" before it falls off plane. I watch how the hull drops in the water and this tells me where to move the weight.

All this takes some patience and is as important as getting your engine shimmed correctly to get the hull to run on top the water with the least amount of drag. I really enjoy the experimentation with a mini because the changes you make are more noticeable than with a high powered setup. Today I was out experimenting with shims(washers), even one washer makes a difference in the way the boat runs. It helps to know your boat and how it reacts in different depths of water. When you get it right you can feel it, moving the stick and feeling the way the boat slides on the water. As I said, you have to get to know your boat before you will notice these changes.

Sorry, I got lost in my little corner of the marching band there for a moment.

[Duane Scarborough]

Papee,

I won't argue with you about that. (keeping the tip above the transom.) I just kinda' worked out for me that way. I won't know how it runs until I finally get it on the water. My intent is to go with a 60" prop eventually.

I am planning to build my cage so that I have the option of moving the rest of the rigging forward or back a bit if needed. (Won't be able to go backwards with the 66" prop though)

I'm trying to be careful that I don't sound like an experienced expert here, but I am more than willing to share information that I've picked up from others, and my own project as well.

That's why I posted that response to Airhead to clear up my mistake.

I apoligize for any confusion I may have created.

Thanks,

Duane

The higher HP setups don't lose much by having the prop below the transom but with the mini s we want to get everything out of them that we can, this means keeping the prop tips above the transom. As far as the clearance front to back, it is whatever your hull "likes" as far as balancing the hull for weight distribution. My hull is long so I was able to put the engine rearward as far as possible. Depending on the hull length and seating setup you may have to move the engine forward a bit.

Having the boat balanced the best you can get it means a lot when it comes to it's overall performance. I have mine balanced for one person because I go out fishing alone most of the time. I have my battery and fuel tank loose so I can move them rearward when I haul another person to even out the boat. I test mine by "gliding" I get on the gas then let off and see how far I can "glide" before it falls off plane. I watch how the hull drops in the water and this tells me where to move the weight.

All this takes some patience and is as important as getting your engine shimmed correctly to get the hull to run on top the water with the least amount of drag. I really enjoy the experimentation with a mini because the changes you make are more noticeable than with a high powered setup. Today I was out experimenting with shims(washers), even one washer makes a difference in the way the boat runs. It helps to know your boat and how it reacts in different depths of water. When you get it right you can feel it, moving the stick and feeling the way the boat slides on the water. As I said, you have to get to know your boat before you will notice these changes.

Sorry, I got lost in my little corner of the marching band there for a moment.

[Papee]

NO problem Duane, since this is a good information thread on a direct drive setup I was just clearing it up for future reference for others. I just got lost a bit in my rant. I don't know everything either, just what works in my world.

[Duane Scarborough]

Easiest way to post is pic. When you are posting look for the browse button, click it and look for the photo you want to upload on your computer. Then click on add the file then submit as you always do. The photo needs to be 800x600 or smaller to use this feature.

Or, you can register to the gallery at the top of these forum pages. The gallery will resize your photos for you if they are too large to post here then link them using tags. I recommend starting a gallery if you are doing a build then all your photos will be in one place.

That sounded easier than the way I've been doing it with Photobucket, so I tried it. Nah, I'll stick with Photobucket. I allready know how that works.

Thanks anyway.

Duane

[Duane Scarborough]

NO problem Duane, since this is a good information thread on a direct drive setup I was just clearing it up for future reference for others. I just got lost a bit in my rant. I don't know everything either, just what works in my world.

Papee,

We're good then. No offense meant either way, and none taken either way.

BTW, did you get the starter/generator setup from Chuck installed yet?

Thanks,

Duane

[airhead]

Thanks guys,
All good info and appreciated. and as far as getting lost in the post: man that was great This shows you enjoy this and i want to get to where you are
Ya'll have agood night now ; ye hea

Jim