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Boat will not plane need a llitle insight

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Once again I need a little help. I have a 12' 6" kennedy hull and what is supose to be a 502 Caddy engine with a 70X40 almost new wood prop. We just took this OLD boat out for our first run. The Keystone Cops did not have anything on us today. When we put this boat in the water two of the four runners on the trailer fell off as well as the side rail. Just when we pulled the trailer up to park it. Please understand there are not any airboats around here in South East Georgia so we drew a sizeable crowd when we just fired this boat up. One of us stayed on the bank just incase. LITTLE did we know. When I got to deeper water I gave it some gas and not much happened so Igave it some more. I hade it turning 2200 rpm and all I did was plow water. I gave it all she had. It would not plane out for nothing. Thats when it started getting harry. I had no more pedal and maxed out at around 2500 rpm. I was plowing a LOT of water when the engine started sputtering, the current from the river caught me and I knew I had to turn around and get back to shore. As I turned the boat I noticed smoke coming from the wiring around the kill switch. The engine sputtered and stopped sideways in the river. Here I am in deep water, fast current, no power and on fire.I just thought how glad I am that I put on a PFD. You all know what was puckered and could cut nails. My head held high I had to be pulled to shore. That behind me. Why wont this boat plane? any hints? Thanks
 
what is the max rpm you can get on dry. might need less pitch or a adjustable composit they seem to be the way to go.
 
Based on your descrition of the trailer and the boat, maybe a good place to start would be to inspect and repair as necessary including a tune up.
 
KJC,

First order of business for you is tune that motor. Cadis are notorious for breaking or jumping timing gears. There are replacement chains that do not break as easily. That can easily cause a motor not to have any punch.

The rig you describe should easily turn the 70" prop. Most 12'6" boats with a 500 / 472 Cadi will easily spin a 72" adjustable wide blade composite prop. Let us know who makes the hull and how wide it is. You may have a problem with a very narrow boat and a car engine..

Max rpm for any airboat prop is 3,000 when it is excellent condition. If the prop is old or has nicks or splits in it, you are taking your life in your own hands spinning it AT ALL.

Look to see if the stringers are solid and not separated from the bottom of the boat. If they are separated, then a hook will form when power is applied sucking the boat to the water instaed of letting it plane off.

Find a very shallow marsh to work the bugs out - or you'll make headlines for sure.
 
I would agree with Big Daddy, fix all the kinks for the boat and on the trailer, with the boat on the trailer. Run her for a while on the trailer, make sure nothing is behind her that will get sandblasted, and that the boat is securely attached to the trailer, trailer to the truck, truck with parking brake set and maybe some wooden blocks to chock the tires.

KJC - I would find shallow marsh to get some practice in on and learn how to handle an airboat for several hours. Then find some place that is about 2 to 3 feet deep to learn the different in the boat's handling in deep water. It might (and probably will handle very differently) in deep water. Some of these boats are dreams in one situation and a beast that requires very close attention to operate in others. If you are in water only 2 to 3 feet deep, the motor shouldn't go under if (or when) you sink or swamp her. Saves alot on repairs.

Good Luck
 
KJC,

Thanks for your kind words. In your reply you state this is a 12'6" X 6'6" older Kennedy that someone has fiberglassed a deck over to. Sounds like this boat has gotten reel heavy. Old Kennedys tend to run on their noses and have a habit of breaking stringers. I've owned two and each has done these things.

The 472 / 500 Cadi should easily spin that 70" stick - unless what it is pushing weighs a ton. That powerplant is a great way to start and learn airboating as engine parts are readily available and many mechanics are familiar with it. Cadis are desirable because they build huge torque before 3000 rpm.

Measure the didtance between the stringers where the engine stand fastens - it should be 36". If that is the case, I have a good 13'6" Gilileo / Phillips hull with slick bottom that you can buy for $1,000. You might be in business for less than you think.
 
BigDaddy,how much torgue do they put out at 3000?I`m trying to compare it to the BUICK 455.
 
KJC : Do you have a death wish ?? Just stop and look at the big picture here GEEZ louise. Your trailer falls apart the engine doesnt run right and your out in the river. I would guess that the maint. on this boat has been lacking for quite awhile. Please take this thing out of service until you go over it with a fine tooth comb and if you dont know what you are combing for park it and get another one that is in decent shape and then work on this one if you want to I don't know why you would want to but at least maybe no one will get hurt that way.

I agree with the others ... buy the different hull swap the engine over and if that prop doesnt look brand new make it into a clock and hang it on the wall while it still is in one piece and doesn't have blood on it.

go find some shallow water nothing over 4 feet deep and probably should avoid anything that looks like slime until you get a handle on that thing and definitely stay away from trees and other immovable objects.

A guy here in florida had always ridden on boats and he finally got his own and headed to the river ... his first run on his own boat he came up on a sand bar (shallow water) from the deep water .. the boat picked up speed quickly slid into a tree threw him off he hit a tree and killed him.

I drive my boat alot and have been doing so for a very long time The other day I hit what we call cow snot on the edge of a pasture .. it was like riding on grease and I was already sliding sideways setting up for a run along a tree line after some frogs .. I did not hit the trees but my girlfriend was less than entusiastic about the next pass I set up to make after the spin I had to use to save our butts on the first one. DOO DOO OCCURS no matter how long you been at it and when it does if your boat is not up to it your in big trouble. There is not time to read an instruction manual or get advice right then.

The KEYSTONE COPS were funny and probably really knew what they were doing and I bet they used the best equipment they could buy or build ... Dont take chances with your life, airboats sink props explode hulls split GO EASY START SLOW and always FOCUS ON SAFETY yours and bystanders .. sorry to preach but GEEZ MAN.
 
cntry - That's not preaching, that is telling the truth.

I have a buddy that ran an old airgator with lots of hard hours on that hull. The side welds had split and they were rewelded (by someone that wasn't a boat man). Jon and I were running down the GIWW (Gulf Intracoastal Waterway a big 14 foot deep channel for tugs and barges all along the Gulf Coast) when the welds split again.

Thank goodness for Rule 2000 bilge pumps and low tides caused by cold fronts. The Rule kept pumping hard and we stopped at mud flat after mud flat to let water drain out plugs (and the split sides). (You can pull the plug on most boats get on plane and water will drain out.) But with that Rule 2000 and two one inch drain plugs draining we would make only about a 1/2 mile and bank it. Took a long time to make the return trip, they were launching a jonboat to go look for us when we returned. If it wasn't for that cold front and the low tides, we would have been sunk in at least 2 feet of water if we would have been lucky.

Those wooden propellers shred into lots of little splinters when they shatter, if they are damaged just slightly and any type of crack can enlarge to boat destroying size in just a split second. Those metal prop guards now become lethal weapons that are coming off the prop. Pieces fly forward, out the sides, everywhere. If the motor is turned up high RPMs, the torque of one blade going to pieces can rip the motor from the stand, then the other blades go, the motor can bounce around, the cage can be destroyed, the stand destroyed, the hull pierced, and the engine damaged.

If it has a minor crack it is only good for a clock mount.
 
Looking back it was not to smart to check this boat out in deep water. We had ran it on the trailer a few times for about 15 min. at a time. We had no inkling that the wiring was messed up. Sounded good. But I will do something I should have done first. Have someone check out the engine and tell me the details. If compression is ok, the year model, and make, to make sure if it is a Caddy. If the engine checks out we will cut the top deck off the and check the hull and stringers. If engine checks out, and you all think this is a good motor to build on. I will probably build this one a peice at a time. If that the case I will be bugging everyone on haw to set one up. First is a NEW composite prop. Thanks for your concerns and all the help.
 
KJC, That's a logical approach. 472 / 500 CU in Cadis were manufactured in the late '60s up until 1974, I think. Later years, a closely similar engine took over the 425.

There are a few folks who specialize in getting tons of torque out of them. support@cad500parts.com has a great Cadi performance catalogue.

They are the beast when it comes to low rpm torque and can function well as direct drive or reduction unit airboat power plants. Parts are more expensive and not as numerous than BBC. Many fishing guides on the west coast of Florida run them box stock, with only a HEI distributor and a new pinned timing gear and chain for years.

Don't feel too bad about the criticism. Most of us started kinda dumb and learned at great expense. Help is here.
 
critisim is a form of advise and all of us can us some advise from time to time. So to all Thanks. I understand what cntry was telling me and greatly appreciate his input as well as the advise from BigDaddy and Marshmaster. I have had the engine checked out yesterday and all was good news. The engine was out of time a little but didn't jump or break a chain. The compression was excellent #150 to #160 in all cylinders oil pressure is verry good. So at least I have a place to start. I will be talking to you BigDaddy. Will that hull do ok in deep water? We will conduct an experiment and cut the top off of the Kennedy hull to verify broken stringers and soft spots for the Hooking you all discribed. I will let you know.
Thanks
 
The Gilileo I have for sale has medium sides.

If I were going to buy a hull for that Cadi engine, it would most likely be a 14' Rivermaster - somewhere arouund $!,800 with Poly - made by Hoffman Airboats (352-726-7677) in Inverness, FL Unbolt your 36" OC Kennedy engine & seat stand and bolt it into the Rivermaster - most likely. You will need a new prop cage as the Rivermaster is much wider than your old Kennedy - that's where the stability comes from.

There's a guy from near here - Greg Abbott - who regularly outruns aircraft powered hunt boats in races with this combo - and he placed second overall in the CCAA Rodeo last fall. A very nimble and manuverable combination.
 
I saw that boat this weekend and it run very very well and I might buy that style hull and put my setup in it.
 
The owner is from New Port Richey and he seems to be a fine example of what we all need to strive for. He is polite, watches his prop wash like a hawk and is very considerate of others. His boat is very powerful and quiet. Mrs. Hoffmann has nothing but good things to say about him. He is a leader in his local airboat club and takes on many airboat related public service tasks.

In addition to all that, he is a very tough competitor with his equipment.

I, too, am strongly considering that set-up for the gator hunt boat I am setting up this spring.
 
We took the top off the old Kennedy hull and found that the stringer under the right motor stand runner was rotten for about 18" at the front, the center stringer was broken,the person that decked the boat used 1/4" plywood for support for the fiberglass mat. It was rotten an waterlogged. It's a wonder it didn't break in half along with catching fire. I have taken your advise and ordered a 15' River Master with new rigging. I will put the Caddy engine on it and try again. Just to let any one know that has a Caddy. The web site that BigDaddy posted here is a excellent site for parts and info. They told me that this engine is a Eldorado Cadillac, 1973, 300 hp, 474 ft.lb. torque at 3000 rpm .Engine is in good shape. I just hope with this new setup things will go a whole lot better. I jut want a reliable boat that will run dry. Sounds like this River Master is good for that. Any sugestions on the type of Composite prop to use. Needs to plane easy, run dry, not interested in a lot of top end. I am thinking of a 3 blade narrow that Hoffmann Airboats is recommending. Any input on noise or reliablity?
Again thanks to all
 
Hope the new hull beats all your expectations and glad the motor is in good condition.

As for the prop. Is that a narrow blade Sensenich? I only have run them on Lycoming aircraft engines, but they really impressed me. Have used those power shift on 350's as well and really liked those.

Those big block guys will see your post and give some hints.

Good Luck
 
Prop choice is your option. Many dealers strongly suggest Sensenich Props. May be because Sensenich has an active dealer program.

Enthusiasts seem to prefer a wide blade composite like the Powershift Maximus or Florida Airprops "Terminator" for larger auto powered airboats.

Large boats and dry ground call for blade surface and push more than "snap". My single observation about narrow blade props is the high pitched whine they make at or near 3,000 RPM. Carrys forever and hurts my ears.

I have seen the 3 blade Sensenich perform great on smaller aircraft powered "hunt boats'. The most impressive auto powered boats seem to prefer the wider blades.
 
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