which engine with this boat and prop

[mark123]

I built a 13' X 7' airboat from Glen-L plans and I found a complete cage/framework with 59" X14 degree pitch (adjustable pitch) 3 blade composite Arrow prop. There is currently a 400hp ford truck engine in the cage but I think that is way too much for me. If I put a 4.3 V-6 chev. in there would it be suited to that prop, would I have to use reduction or 1:1. What about changing the pitch. The seller said he had this setup in the same boat that I built and it would do about 50mph but that it would be very dangerous for a beginner. He had the engine down low in the boat and used a chain drive with 1:1 ratio and mounted the prop about 2' above the crankshaft.

[SWAMPCRACKER]

AS A BEGINNER AND WHO WANTS TO RUN CARMOTORS I WOULD SUGGEST A SMALL BLOCK 350 V8 SET UP AS DIRECT DRIVE...WHICH IS WHERE THE PROP BOLTS RIGHT TO THE MOTOR USING A PROP ADAPTER THAT'S MADE FOR THE PROP.THAT YOU'RE USING ..THE MOTORS ARE EASY TO WORK ON AND PROBABLY WAY LIGHTER THAN A MOTOR COMING OUT OF A TRUCK WHICH WOULD PROBABLY BE A BIG BLOCK OR SMALL BLOCK 400...350'S HAVE PLENTY OF POWER AND WILL PUSH THAT BOAT JUST FINE... IN MY OPINION IT WOULD BE GREAT FOR SOMEONE THATS NEW TO AIRBOATING... I'M SURE OTHERS ON THE SIGHT WILL CHIME IN WITH THEIR OPINIONS...GOOD LUCK...

[mark123]

Would the prop I described work DD with a 350 and this boat?

[SWAMPCRACKER]

Yea I don't see why not...You would more thank likely have to go to a machine shop and see if they can make you a prop adapter to fit on the back of the motor then for the prop to mount to it...Do you know how big the prop is? and how much horse power rating it has and or how many rpm's it can spin??? thats important info to know... That makes a big difference as well...bigger prop more air to push better performance...The motor will have enough power...Just try to keep the weight down just bring only the neccessities...And it will perform fine... hope this helps...

[grant]

59 inch prop will work.....just not very well.

[sberryman]

you will need to call competition aircraft in california and tell them what motor and hp so they can send you the right degree wedge blocks for that application




Competition Aircraft, Inc.
10925 Shire Court
Grass Valley, CA 95949
Toll Free: 888-634-9839
Voice: 530-268-3048 Fax: 530-268-2321
ultra-prop@competitionaircraft.com

[Daddy Dave]

Are you certain its a 400 hp Ford and not a 351M / 400 ci Ford? Lots of difference in the two. If it's 400 hp, then which block is it? Why not run what you have and see how it does before changing everything out? Most direct drive applications similar to the engine size you think you have will turn a 68" or so prop. Lots of folks run DD auto on 13 foot hulls - they aren't hill burners - but you haven't said anything about the water / snow ??? you plan to operate on. For direct drive auto applications, the 472 / 500 ci older Cadillac engines can't be beat. Please put up pictures of the rigging and engine stand - it may or may not be safe with any engine.

[mark123]

The engine was out of an '89 ford truck, an M400 modified, different cam. The seller said 400hp he only wanted $400 for the whole works or $100 without the engine. I just got an e-mail that he sold the motor so it is gone but I think I will get the rest of it , can't go wrong for 100 bucks. It is chain driven at 1:1. Would I be better off changing the sprockets to have some reduction and put a 350 in it. It still needs a safety cage around the prop obviously. I tried to attach some pictures.

airboat cage.jpg (11.36 KiB) Viewed 1200 times

[sberryman]

the three blade ultra is $300 + shipping by its self ----- is the boat alum. ? I would not use any kind of chain drive!!!!!!!!!!!!!! TOO risky .
you can go DD and change the wedge blocks to what ever pitch you need . look in the photo gallerys and get some ideas on the metalwork you will need

[mark123]

Here is a picture of the chain drive prop shaft, I didn't think pillow bearings like that should have a side load on them. How many pounds of thrust would the prop have , ballpark figure.

[mark123]

forgot the picture, also the boat is plywood with fiberglass covering. The plans for the boat are at https://www.boatdesigns.com/products.asp?dept=469

[yobee]

That chain drive is scary! Ill watch from shore... behind plexiglass lol.

[SWAMPCRACKER]

yea definately think about getting rid of that chain drive setup...Go with a direct drive setup if not you'll risk breaking the chain sooner or later and have it go thru the prop or the boat itself...Take all that off and have a machine shop make a prop adapter that will bolt to the prop and then to the motor...from the pictures you might want to rebuild the motor stand and get it higher " centered " so you can evenly swing the prop in the cage...The motor is way to low in the boat for a direct drive setup...also do you know how wide the boat is in the rear? because I would suggest a bigger prop than 59"s I would try and fit a 66" being the smallest up to how ever big you can fit in the cage while clearing the cage all the way around...How strong is this boat you said its plywood with glass layed over? man I would be careful and make sure you have enough support where needed...Also what type of terrain are you going to be taking this boat? river,lake,glades,snow ? be careful of rocks thats for sure...hope this helps...

[Smuggler]

That chain drive is scary! Ill watch from shore... behind plexiglass lol.

Yobee make sure you leave enough room behind the glass for my big a$$ as well I can't imagine what that all looks like turning 3,000 RPMs I'm with these guys.. Build a new engine stand for DD for now..

[mark123]

Why is the chain setup so scary, don't most street bikes use it and they turn up way more than 3000 and some have 200+hp. Isn't the idea of having the engine down low better for center a gravity, less chance of tipping over? Much easier and cheaper to change gearing ratios, much cheaper than belt or gear drive reductions. Or how about 3 or 4 groove B belt pulleys and belts?
I am not second guessing anyone, I just want to understand this better.

[THE NIGHT RIDER]

BUDDY YOU NEED TO START ALL OVER, THAT CHAINDRIVE IS WAY PAST SAFE . AND THAT HULL IS GONNA BE ANOTHER STORY . I SEE YOU DONT HAVE MUCH IN IT BUT WHAT YOU HAVE LOOKS HAZADOUS TO OTHERS. JMO U NEED TO START WITH SMALLBLOCK CHEVY AND BUILD NEW RIGGIN AND PROPGAURD .YOU HAVE TO DO IT LIKE MOST OF US DID .ONE PEICE AT A TIME.IT TAKES AWHILE BUT IF YOUVE GOT FAMILY U LOVE AND WANT TO ENJOY RIDING WITH YOU NEED A SAFE MACHINE. IF YOU LIVE NEAR COCOA I CAN HELP YOU WITH NEW ENGINE STAND SEAT PACKAGE AND GAURD JUST SO YOU WONT KILL ANYBODY WITH THAT SETUP.

[THE NIGHT RIDER]

SORRY I DIDNT NOTICE WHERE YOUR FROM I CANT HELP BUT YOU NEED SOMEONE TO.

[Smuggler]

Why is the chain setup so scary, don't most street bikes use it and they turn up way more than 3000 and some have 200+hp.

Yep your right street bikes use it HOWEVER between the rider and the bike what are we talking.. 500-600 lbs?? So that chain is able to move that weight easily.. On a airboat your talking at least 2,000 lbs your trying to move plus you don't have wheel bearings to help it roll.. I think the general consensus is the amount of thrust it takes to swing a prop is WAY more than a chain/bearing set up of that design can handle. Myself I wouldn't try it!! However if you do decide to give it s shot anyway.. I would make some sort of guard for the chain.. JMO

[Rich Andrews]

might make a good table saw??