• If you log in, the ads disappear in the forum and gallery. If you need help logging in or getting registered, send request to: webmaster@southernairboat.com

More on prop angle

papee

papee

Well-known member
A little info first. I live near Harrisburg, PA. My rig is for fishing in very low water at spots, well, of course I don't fish in the low spots(only a few inches).
I chose to go with a small engine, an 18 hp B/S twin cylinder. This setup take much less water when floating in the low water. Right now I'm using a wooden prop I made and will soon change to a CF three blade prop. The boat is a 16x6 alum.

Today went out fishing for a while then decided to experiment with the prop angle. I started out with it at a right angle from the stringers which was not the best, it ran better before. It will plane out if I find lower water. I'm staying in deeper water for these experiments.

First I adjust it using a thread rod setup I have on the rear of the engine to raise or lower the rear higher or lower than the prop side of the engine. The boat seemed to work better coming close to planing within about 20 feet. it came up pretty level but then the front end lifted and would not come out of the water.

Next I lowered the back end or pully/ pullstart side to keep the nose down. That setting was worse, so I deciced to adjust it to push down on the front and lift the rear. This setting was worse than the rear just slighty lower than the prop side.

I am thinking that if I get the best adjustment with this prop it should be pretty close with the new prop. My thinking is that with this prop, the adustments are easier to tell than when the new prop is on.


I'm looking for your ideas on which would be the best way to adjust to keep the front down or am I at my limit with this setup? I would like to get the most out of this setup before going to a larger engine adding more weight.

Sorry for the book but I wanted to give as much info that I could.
 
With my hull level.Using a level on top of my motor I am a 1/4 bubble off to the front of my motor.Basically I'm lower at prop end.A lot of guys run level with hull,that doesn't work for me.
 
Your on the right track adjusting, just go to what ever one worked best after you ahve tried a few different ones. You may be at the limit of what you can do with what you have so just go back to what was best and that is all your gonna get. if you wnat more change motors and or drive units and start adjusting all over till you find what works best for that one. there is no set answer for every boat they all are differnet.
 
Sounds like you got a good handle on it the way your doing.
like any adjustment, make your adjustments in small increments
and record each change. I've only owned two air boats and never
had to make that kind of adjustment. But it seems like a good
place to start would be with the prop at a 90 degree angle to the
bottem of the hull. Good luck and have fun. KEVIN.
 
Papee, my 2 cents. You mentioned that you might be getting another prop. If you do, hopefully it'll give you a little more push. When you install it I'd go to a belt reduction unit at the same time. Several people make them for the B&S twins, and then you can put on a little bigger prop than you originally had in mind for your direct drive.

Those two together should make a big difference in the way your boat performs. Remember too that more thrust means more stress on your engine stand, so look that over good in case you want to add a little reinforcement to your setup in the process.

Olf
 
Papee, Welcome aboard!!

Skeeter admits it......he's a quarter bubble off.....From what folks who know me say, me too.

If you need some professional advice on that B&S rig, Paul Dixon at Seminole Airboats in Bainbridge, GA sells a similar outfit.
 
Thanks for all your help guys. I would guess it's just our nature to tinker. Mine anyway :lol: My thinking was that if it comes out of the water in the low stuff I could "tweak" it to come up all the time. As was said, I think this is all the setup is capable of. I'll get the new prop, then see how it goes.
 
Just to keep this all in one place I'll do my thinking out loud here. After another weekend on the river fishing, dreaming up ideas to make this thing go, I've come to a decission. I noticed that the "push" was gone before I hit full throttle. I'm not sure of the rpm but I noticed the push was done at about 3/4 throttle. I'm guessing about 2600-2800 rpm.

I'm going to redo my cage and engine stand to accept a new 48 inch three blade carbon fiber prop. I'll put the new prop on and see if the 18 HP will turn it, if not, I'll just move up to the 35 hp engine. I'm running a 42 inch heavy home made wooden one now.

I figure any new prop will be an improvement over what I have now and if I'm getting a new prop I may as well get one that I can use on a larger motor because we all know that is next.
 
Papee,
You should call Paul Dixon before you spend your money. He probably has some real good advice.

Do a forum search here for keywords " small airboat" Mini Airboat" ext.

There are some really good threads that covered allot of this info, and had links to videos of briggs / kohlers running dry mowed grass.


Check it out.
 
Thanks, I will be contacting him in the near future. I see that he is running wood props on all of his though. I'm hoping it is just a cost thing. I've been told to get away from the wooden prop because of the weight. On the other hand, I've been told by others that I should stay with the wooden prop for my engine or up to 30hp. I'll listen to anyone's ideas. This is an obcession for me with these small engines. My last one was a 14 ft with an 8hp that planed with two people on. I got some looks with that setup :shock:
 
I think the micro-boats are cool man.
I'd have one... but one more vehicle in the yard, and my wife will open fire!
 
Florida boy that boat is lookin good I bet you will be happy for a while with it. HOWEVER I should warn you the disease is almost always permanent once you catch it and there is no known cure LOL have fun
 
You must log in or register to reply here.
Back
Top