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Thread: Flathead's Combee TomCat

  1. #1

    Flathead's Combee TomCat

    I've moved my post to this forum for obvious reasons. V-dub motor = automobile engine. You know what was funny? A couple of days ago I was browsing through a VW engine rebuild book and the author stated "Your VW engine will give years of reliable service provided you remember a Volkswagon is not an automobile, it's a Volkswagon". So, if a Volkswagon is not really an automobile, then is it's engine an automobile engine? Just kidding.

    Here area few pics of what I have and what I have done. It appears the boat was in some type of accident before I bought it. The cage was canted to one side and you can see one where the prop tip sheared right through the cage. Kind of scares me a little. Fixed that up with a come-along. Just pulled it back into shape.

    The accident mangled the prop tips a little, so I ordered a Ultra prop from competition. Should be here in a few days. In one of the pics you can see a hex shaped extension to elevate the cage about 1.5 inches. That will allow me to run a slightly larger prop diameter safely. I'll be trimming the prop myself, so I hope to end up with a 54-55inch prop. We'll see. I have a variety of pitch blocks coming, so hopefully I can get her dialed in pretty quick. The boat tachometer is off a little. it reads the engine rpm's are about 400-500 faster than what the actually are. I confirmed this with an ancient dwell/tach meter I found at a local snowmobile swap meet.

    I'm hoping the new prop will get me onto plane. I'll feel much more comfortable starting the rebuild project this winter knowing I have a good motor/boat/prop combination.

    Bruce

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  2. #2

    Re: Flathead's Combee TomCat

    Just a few more pics:

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  3. #3

    Re: Flathead's Combee TomCat

    and one more!

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  4. #4

    Re: Flathead's Combee TomCat

    Flathead,

    Now I see that the air intake was hooked directly to heat. This makes me think that there was definately some kind of issue with the performance. I have never seen or heard of this. I would be sure the heat tubes are working and that the carb is doing it's job correctly.

    Jim

  5. #5
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Re: Flathead's Combee TomCat

    Flathead,

    For what it's worth, I don't care one bit that you've got a VW engine.

    You've got a nice project going there. I'm looking forward to seeing your progress.

    Thanks,

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  6. #6

    Re: Flathead's Combee TomCat

    Ditto to Duane :P

  7. #7
    Senior Geezer buster's Avatar
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    Re: Flathead's Combee TomCat

    Add one more ditto to that . Unless they are going to compete (Race), an airboat is an airboat the way I see it, and the small ones are more affordable.

    Dave
    IF YOU WON'T STAND BEHIND OUR TROOPS, THEN JUST STAND IN FRONT OF THEM!

  8. #8
    Member
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    Re: Flathead's Combee TomCat

    Hey Flathead , cool looking little hull. Side by side seats look comfortable.
    Looks like you got a good little project. Good luck. I hear if you want to spend some cash you can get well over a hundered Hp out of a VW motor.
    Bogger
    Boat specs:
    Hull, 116 fiberglass
    Bottom, Frog spit
    Motor, Rotax 532 dual carb
    65 ponies to push with
    Reduction, 2.58/1
    Prop, IVO 62in.3blade adjustable
    Rigging, 0.5 and 0.75 emt

    All still under construction

  9. #9

    Re: Flathead's Combee TomCat

    100hp? Holy cow! Look, up in the air. Is it a bird? It it a plane? No! It's flathead's Combee Tomcat! hmmmm, Maybe I could retrofit a set of ultrailight wings on it

  10. #10

    Re: Flathead's Combee TomCat

    Naw bad idea

  11. #11

    Re: Flathead's Combee TomCat

    OK. Performance results with new ultra prop. 1st trial run I trimmed the prop to 54inches and used 14degree pitch blocks. ran up to about 2700 rpms at wot. boat would not plane I got 8mph per my gps. Did not run it in shallow water.

    2nd trial. Trimmed prop to 52 inches and used 16 degree pitch blocks. got about 3100 rpms on the trailer and about 2800 in the water at wot. boat would not plane in deep water but would stay on plane if I got it on plane in shallow water. However, it would not sustain plane with 2 people in boat. 9mph in deep water. 21mph when on plane.

    More trials monday, I'll keep you posted. I think I'll trim the motor a little before changing the prop set up any more....

    Bruce

  12. #12

    Re: Flathead's Combee TomCat

    Hey Flathead,

    I agree with you about the shims. It's harder to put length back on the prop But seriously I hope you get going right without much trouble.

    And how's VW doing?

    Jim

  13. #13
    Administrator Papee's Avatar
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    Re: Flathead's Combee TomCat

    I'm thinking you may have a weak motor, I'm turning a setup almost equal to that with my 084 at 57x 10
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  14. #14

    Re: Flathead's Combee TomCat

    Hi friends,

    Results of monday trials: So I thought the motor may need trimming because the rear end of the boat really pushes down when I get on the throttle. When I checked it though the prop seems to at 90 degrees to the bottom of the boat. (I leveled the bottom of the boat, and then checked the hub of my ultra prop and it looks whiskey-eye square) In the spirit of every boat being different I assume the ideal angle would be about 90 degrees. Any input on that assumption?

    So instead if trimming the engine, I moved the battery and gas tank to the bow of the boat. It helped. Now the boat will plane out in deep water with one person (225lbs) It does not shoot out of the water, but it will plane out in about 200ft. Still will not plane out with 2 people in deep water (425lbs) nor will it sustain plane if I get it on plane in shallow water.

    My tachometer reads about 2900-3100 rpms and I know it's 400 rpms off, meaning it's really running 2500-2800 rpms so I may try a set of 14 or 15 degree pitch blocks. That should get me up around 3100-3300 rpms which is about as high as I care to go.....direct drive and all.

    I agree with you Papee, I also suspect the engine is a little tired. However, it seems to be running a little better every time i run it. And I see what you mean about needing lots of oil... Looks like I'll be learning a lot about these motors.

    By the way, interesting observation: The motor revs faster stationary on the trailer than it does moving in the water. There's about a 300 rpms difference. I seem to remember this coming up before somewhere in the forum.

    I think I'll go install thise 14 degree pitch blocks now and see what happens.....

  15. #15
    Administrator Papee's Avatar
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    Re: Flathead's Combee TomCat

    That's the attitude! Tinker. Once the boat is on plane you can tell better what the engine needs for shims. If the bow rides high put some back shims in. I set mine up for best performance with just me in it because I don't haul other that much. Nobody likes to got out fishing with me because I stay too long. LOL
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  16. #16

    Re: Flathead's Combee TomCat

    Head Flathead,

    Things are sounding better If the engine is feeling stronger maybe the rings are freeing up. That is if it has been sitting up for a long time. If that is the case you may want to try putting some marvel mistery oil or something similar in the spark plug holes and let it sit a few days. I would put a bunch and blow it out before next trip. The worst than can happen is fouling some plugs. Just a thought

    Jim

  17. #17

    Re: Flathead's Combee TomCat

    OK. Last post of the day. I gotta get some chores done and quit playin' with the TOMCAT. I know in my last post I was going to try the 14 degree blocks. However I figured that would only increase my max. rpms about 200rpms. I think 3500 rpm's is about max for my setup so I went all the way and put in 10 degree blocks. WOW! what a difference. The boat comes right up out of the water and cruises on plane easily. I did not have my wife with me but I'm sure (knock on wood) it will get us both out of the water. (plus a beverage or two). Now it seems a little nose heavy so if it runs OK with my wife in it, I'll move the gas tank back to the rear of the boat.

    Current set-up 52 x 10 3 blade ultra prop. 3400rpm's at WOT. 1600cc 50ish hp VW motor, direct drive. I'll bring my gps next time to get some reliable speed figures.

    Bruce

  18. #18

    Re: Flathead's Combee TomCat

    Congrats Amego

  19. #19

    Re: Flathead's Combee TomCat

    Well, it was good for a while. The boat would come onto plane and run 26mph at 3400rpms in open water with one person in it. I could even back off on the rpms and stay on plane. It was able to get my wife and I on plane as well and run about 21mph but I had to keep my foot in the carburator the whole time. After a couple of minutes of this the motor started to bog down. Overheating I'm sure......couldn't get it to restart until it cooled a little.

    Looks like a psru is in my future. However, the ones I find online cost more than my boat, trailer and new prop put together. UFTA! I'm a machinist in my other life and I'm giving serious thought to building one........I wanted a project and I got one!!

    I've looked online but have not been able to find information about what is a reasonable rpm range for that VW motor. Dual port, 1600cc type I. Maybe I'm pushing it to hard. Anybody have any input?

    It's all good.

    Bruce

  20. #20

    Re: Flathead's Combee TomCat

    You're definately not pushing it too hard. I wish we lived closer i would love to help you get it right.

    Jim

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