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I need your expert advice.


Active member
Time to grow,and deferring to the experts for advice on some of my challenges. In 1978 I built my first Air boat. I built it off the recommendation of Banks Maxwell (Propeller Manufacturer who sold to Askey). I built a aluminum hull 6061 T6 fully welded. The hull size was 16 foot long with a 54 inch bottom and 18 inch gunnel's. I live in Oregon and the terrain I ran it over included deep water, mud, tree stumps, steel fence posts, rocks, and submarined it once. After 28 years of this abuse the boat still runs like a champ. Never being able to leave it alone I have reconfigured the seating arrangement four times and rebuilt the motor twice including turbocharged. After all the changes over the years I found the stock corvair engine with the nitrided (turbo) crank, compression dropped to 8.5,, and stock 1965 carbs to work the best. I continue to run the Banks Maxwell prop 60 inch diameter at 28 degree pitch (noisy) but effective when turning above 3000 rpm's. This boat allowed me to collect more duck and geese bands that any of my hunting friends over the years. The problem is things are changing in Oregon, we have a lot of people canoeing, the noise is objectionable to our law enforcement community, and I am unable to run dry ground!!!
Time to grow: I clearly understand after reading numerous posts on Southern Airboat you guys are the experts. Based on the information in the majority of posts I believe the GPU 220 to best the best choice for a power plant (which I purchased last week). The best choice for a prop would be the 72 inch Sensenich two blade Q (which I have not purchased at this time). Down to my main concern which I hope you guys can help me with. I need to choose a hull which I can run deep water chop as well as dry ground. Due to the issues I mentioned above I must run a minimum of 200 feet from the bank when running on the major waterways here in Oregon. This places me in water over 200 feet deep with 3 foot swells to get to my hunting spots.
I purchased a special rapid runner hull which is designed to race upstream over rocks and small waterfalls. The hull is made of Kevlar and weighs about 800 pounds. I am concerned since the bottom width is only 60 inches with sides flaired out to 80 inches, the length is 16 feet, and gunnel's are 20 inches ( I am concerned the boat may be top heavy with the 220 and a 60 inch wide bottom). This is where I hope your continued expertise can help me. We have a very limited choice of hulls here in Oregon. What type of hull would best suit my needs with the aforementioned power plant? Any advice would be sincerely appreciated.
the only concern i would have with the hull you describe would be tq roll at deep water starts ,if your rerigging it just try to build a little more wt away from that side to compesate tq 800 lb hull sounds heavy to me for a 220 to run alot of dry but it can be done ive seen em run dry with 4 grown men and gear
If you want to help eliminate torque roll go with a 3 stringer boat that has narrower runners I think like 24 inches not sure it will allow more play for torque in deeper water .Spreads the torque out a little more with the weight of the motor closer to the center of the hull
Gentlemen, Thank you for your help. I did not think of the torque issue, which was not a problem in my small boat. Thank you Plumcrazy for the heads up. Do you believe the 60 inch bottom would be wide enough? I can remove the side stringers which are laminated 3 inch by 3 inch oak 3 on each side and cap the rail with an aluminum stringer this would remove about 200 pounds from the hull shifting the weight down in hull. The edges where the bottom meets the sides are extra reinforced as well. This was a rapids racing hull so the bottom and sides had to be bullet proof to bounce off the rocks at 60 to 70 miles and hour. Mr. Conr520 you mentioned three stringers at 24 inch spacing. In total the width of the bottom of the boat would have to be in excess of 72 inches which would eliminate the hull I have. i am not locked into this hull, although it is one of the widest flat bottom hulls I have found in Oregon, do you recommend I discard this hull and keep looking?
Thank you for sharing your wisdom with me,
im the kind of guy that will work with what hes got thatshull is about the same dementions as a old airgator i had acaddy motor on an i nerver sunk it but it did lean when i poured the coal to her it must suck to build a boat up in the north west, down here thers a used hull behind every tree :?
No thats 24 inches total of 3 stringers Outside to outside with 12 inch spacing so your hull would work . Just would have to rearrange your stringers all is good
if you can take wt off it and it still be strong id do it airboats are like planes the less they weigh the better they perform also i like a ww signature series prop
plumcrazy":2inbsz4t said:
if you can take wt off it and it still be strong id do it airboats are like planes the less they weigh the better they perform also i like a ww signature series prop
This I agree but make it practical for your application I also run a ww prop ,but sench.makes a good product as well

Heres a thought. Move to Florida and build you a boat here. Lot less obsticles and super deep water to deal with. Theres a beer factory in every 3rd town and we do a lot of rides. Everybody else is moving to FL so Id a heap rather see airboaters moving in than dry dockers and flat landers from the North East.

Scotty :wink:
Gentlemen, again thank you for your wisdom. Yes it is a challenge in the Northwest to build an adequate airboat, although the rewards are great since it gives a person access to all the best hunting without someone 50 yards off your gun barrel. Mr. McCormick, thank you for clarifying the stringer dimensions for me. I will definitely follow your advice. I was under the impression the Sensenich 72 inch two blade Q put out the exact same thrust as the Water Walker Signature series, with the only difference being the Sensenich was quieter. Was I miss-informed? With both of you two fine gentlemen recommending the Water Walker is their something I should know?
Thanks again for all your expert advice.
10-4 whitebear but ive been up there the ground is almost allways wet rains a whole lot in parts of the upper northwest we could unload any where an run if the law didnt catch us :D
They Both perform about the same its all in what you want I would probably have a sench if I didnt already have a ww . And Your welcome for the advise its just a thought you could look into and see if thats what would be practical for you :D
the swept blade is a little quieter but i like the push of the water walker, but the seninch performs well to guess u could say its a personel preferance ive tryed em all and for my stile of running i like the signature, us fl boys are very opinionated as youve probaly read
my first boat had a 4 ft wide flat bottom on it with a 220 power plant.had no problems with it . it seemed to run dry easier than a wide bottom boat, i figured it was because their was less of the hull sitting on the groung.it haad high sides ,and ran it in deep water with eas. never had no problems with ruff water.i like the sensenich 70"q prop for the 220 motor.my first hull was very heavy it was 13' x7 with 24" sides the whole boat was made out of 190 alum.it took 4 men to turn it over to put polymer on it .it ran great with a 220 . i put a three blade h sensenich on it .it would run dry with 4 people on it.
Thanks for the invite Scotty, although I don't know if my webbed feet could take the humidity. You guys would own Oregon if you brought your rigs up in the 29 years I have run my small airboat I have never run across another one on the water. I have viewed a few on trailers going down the freeway. The problem here is I have to leave to go hunting at least a half hour early if I am going to gas up. That's how long it takes to answer all the gas station attendants answers as well as the other customers. I am not real popular with Johnny law either since I can stay out of his reach. Mr. McCormick I appreciate your feedback on the Sench.
Thanks again gentlemen for all your support.
thats it im movin to oregon think i got som family in washington wait dont it get cold up there :shock:
Thank you woody for the added confidence, you guys are champions and if you ever want to bring your airboats to Oregon, you can be my guests. Cold in the Northwest? Nothing like spinning doughnuts on the ice.