Results 1 to 9 of 9

Thread: Newbie- why won’t my boat go

  1. #1
    Forum Reader
    Join Date
    Jun 2018
    Location
    Highmore, SD
    Posts
    4

    Newbie- why won’t my boat go

    I am new to this and very frustrated. A few years ago I started getting parts to build a mini air boat for my son. I’m not into boats or fishing, but like a good project. 12’ aluminum hull with poly, weighs 800 lbs, 4A084 engine, reduction drive, intake, Mikuni carb, headers IVO 64” adjustable prop. I got all the parts from Chuck at Air boat Pros. He’s been very helpful, but haven’t been able to get ahold of him. It took 7 different technicians to find someone to get the carb tuned right. Finally an aviation mechanic got it running like a top, BUT it just won’t Go !! Makes a lot of noise, but doubt it goes 7 mph, won’t run dry land. Goes pretty good on ice. I can set it to run 3,600 rpm, but presently set pitch so it max’s Out at 3,300. It just won’t go. I’ll try to post pics and have a walk around video. I need help. My son and I just want to get it going so we can sell it.
    Attached Images Attached Images     
    Last edited by SDtex; 06-24-2018 at 01:03 PM.

  2. #2
    Super Moderator Corky's Avatar
    Join Date
    Jul 2014
    Location
    Susquehanna river, Dauphin, Pa
    Posts
    1,303

    Re: Newbie- why won’t my boat go

    OK I'm going to be brutally honest...
    The hull is way too heavy for the 084 no matter what you'll do to it...
    Most hulls for the 084 are in the 200lb range and some still won't run dry{say the engine is 150,reduction is 50 that's 200 leaving 400lbs hull weight for your rig}...So you either need to change the engine or lighten the hull load significantly...It's the general consensus a poly bottom in itself is too much weight for the 084 and so the reason for everyone using slick bottom on them..
    How is the engine angle in relationship to the hull ???
    I'm assuming you know Chuck was diagnosed with cancer and has closed shop to spend some time on the road traveling/quality family time?

    Aluminum .120 14' X 76" hull
    Teledyne 4a084-4 engine
    Circle S 1.69:1 reduction
    67" Whirlwind "Razor X" prop



  3. #3
    Forum Reader
    Join Date
    Jun 2018
    Location
    Highmore, SD
    Posts
    4

    Re: Newbie- why won’t my boat go

    Quote Originally Posted by Corky View Post
    OK I'm going to be brutally honest...
    The hull is way too heavy for the 084 no matter what you'll do to it...
    Most hulls for the 084 are in the 200lb range and some still won't run dry{say the engine is 150,reduction is 50 that's 200 leaving 400lbs hull weight for your rig}...So you either need to change the engine or lighten the hull load significantly...It's the general consensus a poly bottom in itself is too much weight for the 084 and so the reason for everyone using slick bottom on them..
    How is the engine angle in relationship to the hull ???
    I'm assuming you know Chuck was diagnosed with cancer and has closed shop to spend some time on the road traveling/quality family time?
    No, I didn’t know about Chuck, he was a wealth of knowledge, prayers to him and his family.
    Honesty is what I want. The engine is pretty much perpendicular to the hull as close as I can tell. What’s your best advice.? Remove the poly and see what difference it makes?

  4. #4
    Super Moderator Corky's Avatar
    Join Date
    Jul 2014
    Location
    Susquehanna river, Dauphin, Pa
    Posts
    1,303

    Re: Newbie- why won’t my boat go

    It's tough to say just what needs done without a video of the boat on the water...Wether it's something that can be corrected by moving some weight around to get it on plane or just too heavy is anyone's guess without more input....One thing for sure any weight that can be eliminated is a good thing...If you're just looking to sell it I'd start taking off anything that isn't truely needed...I'd hate to say "take this off" just sitting here typing knowing how much more work you'll end up needing to do but yes, the poly would be one of the items on the list to lighten the load...
    Secondly, there appears to be quite a bit of obstructions in front of the prop..Double wide seat,gauge console, etc... It all adds up quickly for such a small engine to overcome...
    The boat appears to be well thought out and built, we probably wouldn't be having this conversation with a bigger powerplant...Each build really should have it's engine size in mind through out the whole process and the 084's performance will fall dramatically as each component is "overbuilt" for the application adding weight..I'm guilty of that as well...
    Let's start at the beginning so other members can add any suggestions and input to get you where you need to be... such as : Hull width, aluminum sheet thickness,poly thickness, Prop cage building materials and tube diameter,fuel tank size etc... Just to have some info on what we're looking at in general
    Last edited by Corky; 06-24-2018 at 11:12 PM.

    Aluminum .120 14' X 76" hull
    Teledyne 4a084-4 engine
    Circle S 1.69:1 reduction
    67" Whirlwind "Razor X" prop



  5. #5
    Junior Member Bart's Avatar
    Join Date
    Dec 2015
    Location
    Valdez, Alaska
    Posts
    574

    Re: Newbie- why won’t my boat go

    one thought, in looking at the carb setup?? with 2 extra hard 90's before it goes into the stock intake. a lot of your fuel may be dropping out of the air flow. and may be washing into the 2 front cylinders. and leaving the rear 2 cylinders on the lean side.
    a couple of questions.
    what kind of sensors do you have?
    how is the compression, on each of the cylinders?
    what do the plugs look like?
    what are the head temps. running at?
    i know a few have taken the stock intake plenum and cleaned up the inside casting. to help get a better air/fuel mixture to the rear cylinders.
    just asking some questions.
    i would try a top mounted, modified intake, there have been a few different carbs that have been proven to work with this setup.
    your Mikuni carb could might work also. with just one 90 dropping it down to the top. (but you still have that extra 90 that is in the equation)
    i still haven't got mine going yet, but a couple of winters ago I made myself, just a few different intake set-ups to try out.
    if i ever get caught up on some of my projects, i can get this back to the front and center.
    most of the active members on this forum have gone to installing a solex pict 34 carb on an modified intake,

    Bobby has taken the modified intakes and carbs to the next level. but with the help of an wide band sensor, & head temps & gauges. he has been able to know exactly what and where he needs to make adjustments.

    yes, there is some weight on the boat, i like the picture of it on the truck scale. it took me a minute to figure out why and where it was siting on the ground.
    yours is the first one that i have seen, that have posted a true weight. i think many would be surprised if they found out what their mini actual working weight is.
    it looks like you have 2 red fuel tanks also, at least to me that is what it looks like, how big are the tanks, and where they full of fuel. at 8 lbs. a gallon, that might account for some of the weight.
    would you know how thick of aluminum that this was made out of? last winter i had a chance to purchase a mini hull, but upon asking about it. it was almost the same as my narrow one and made out of 3/16" plate, it is amazing on how much that adds to the weight.


    i know, the last thing on you mind is to spend more money on this, but with it running as is. it will not be a fast mover.
    there have been a few others that have built a mini airboat, with the 084 motor, and when done, they got frustrated that the motor would not perform. and when they dropped it. i never seen any gauges or data on what was the problem. to me it was kind of sad, that they would spend all the time and money to build it, and not put on a proper gauge to know what the motor was actually doing.
    where others with the proper tuning, have really enjoyed their project.
    last summer I chased a problem on mine all summer long, and finally figured out one of the chokes was leaking just a little bit on my 2 stroke motor. once if fixed that it ran sweet.
    Last edited by Bart; 06-25-2018 at 07:01 PM.

  6. #6
    Forum Reader
    Join Date
    Jun 2018
    Location
    Highmore, SD
    Posts
    4

    Re: Newbie- why won’t my boat go

    Thanks Bart, I appreciate the input. I didn’t like the sharp bends in the intake either, I got it from Chuck. One tech told me it’s sized big enough that that should not matter about restriction, but I understand what you are saying. It runs like a top, revs up good and smooth. I could use my infrared heat gauge, but all cylinders seem to warm up the same. The plugs are one step hotter than standard and look like they are burning the same.
    I believe it’s just a 6 gallon gas tank. The red tub under the seat is actually a cattle lick tub we use for storage. I doubt it weighs 4 lbs.
    The bottom of the boat is 1/8” and the sides are thinner. I guess if it won’t run dry ground I could take the poly off. It should weigh slightly over 100 lbs. I’ve seen boats on the net with the same engine and big padded seats, electric winch on the anchor and a trolling motor. They’ve gotta weigh more than my boat !!
    Part of the problem is I have no interest in fishing or boating. I’ve never road in a boat til
    I got this one. I live in central SD and I only know of one airboat within 200 miles. Our adopted son loves fishing, sure didn’t get that gene from me. I wanted to build something cool and different, just didn’t know it would take so long.

  7. #7
    Member
    Join Date
    Oct 2016
    Location
    jacksonville fl
    Posts
    311

    Re: Newbie- why won’t my boat go

    the first thing i would do is take off the poly. that really slows a boat down. next run a pipe straight as possible from front of intake to carburetor. i think a member named steve had his that way and it ran great. he only had a slight bend in the pipe. chuck had good luck with the ivo prop. after buying my razor x i wouldn't buy an ivo for any amount. i like the ultra prop a lot more. even a wooden prop should make it run good enough to sell. right pitch of course. if you do take the poly off you need to seal the bolts when you install them. use oval head cap screws. sure is a nice looking boat. it just takes time to get one right. just a few degrees up or down of the engine can cause a boat to be hard to plane. get rid of as much weight as possible.
    Attached Images Attached Images  
    Last edited by bgmcl60; 06-28-2018 at 11:44 PM.
    4a084
    Arrow belt drive
    marty bray 116 mini pro
    solex 32/36
    weber 32/36
    solex 34 pict 3
    weber 34 ich
    Razor x 3 blade

  8. #8
    Junior Member Bart's Avatar
    Join Date
    Dec 2015
    Location
    Valdez, Alaska
    Posts
    574

    Re: Newbie- why won’t my boat go

    here is an idea of what you could do for the intake, like what Bobby was talking about.
    on the elbow that i have to put on top. the flange i left room for 3 different mounting positions. for the elbow i bought an some tubes from saturn surplus, that was about the cheapest place i found to purchase bent aluminum 90's with the 1-3/8" outside diameter.
    and i included a picture of how i cleaned up the webbing on the inside of the casting.
    an intake set up something like this would clean up a lot of the air flow restrictions. and with the fuel dropping in from the top. you should see some improvement.
    do you have any information on what jets and setting that your carb was dialed in with?
    your carb may need to be adjusted slightly again. with this set up there is only about 5 to 6 inches from the top of the intake to the flange on the 90.
    and you could shorten it up even more by attaching an elbow directly to the top of the intake. if you wanted to.
    just a couple of ideas.
    good luck with it all
    Attached Images Attached Images    

  9. #9
    Member yamahaulerG1's Avatar
    Join Date
    Dec 2009
    Location
    lake Okeechobee, FL
    Posts
    126

    Re: Newbie- why won’t my boat go

    I would focus more on weight and your prop. If you are turning your motor 3600 with a 64" ivo the motor is probally not the problem. Sounds like it might just be to much weight for the ivo to push. Seems like the ivo has problems with heavy loads maybe a warp drive or ultra propII would work better. I've seen a few hulls like that one and they are usually heavy duty for hunting dry ground with 150-200hp 4cyl aircraft motors.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •