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pushing on the nose

Southern Airboat Gallery Archives

3 A south 8-11-2007
South of Hwy 50
Removeable jack
new_pic_rigging
518
D-BREWSTER at Jessie Willie camp
c chardt

c chardt

Well-known member
Boat runs good and rides good,But porpoises,Put a trim tab on and fixed that problem, Level the the stringers prop is hub is level.But when running fast it pushes down on nose hard enough I lift on the throtle . Even if trim tab is picked up so,Should I shim the rear of the engine up, and how much would be recommended. Only when I go fast.
 
cc- yep, beware of that at high speeds. Having a boat pushing nose down while doing turns can cause the back end to whip around really fast if you are not careful. I know of one Panther that noses at WOT badly. They stood on the throttle in deep water for a minute just one time, but never again, just because it will plow very badly.

We put a rubber grummet under the rear mount on the 0-540 I run and that solved it. It would only do it at higher speed after we changed out some dry rotting motor mounts. This caused it to porpoise slightly but the trim tab solves that.

While it is a pain, I would try short lifts instead of anything major.
 
I only tryed it in about 1 ft of water.it cruises relly nice in deep water and handles good. so i'll never how fast it will go.
 
You might want to look at the stringer / transom joint. What you describe is often called a high torque hook. It happens most often when a "poscket " develops just forward of the transom and the suction makes the bow plow. Scary. I had this problem on a Kennedy hull and was never able to solve it.
 
try lowering the rear mount 1/4 inch at a time (prop end of engine)
i like having 1 inch of rise on the engine. it helps lifting the
rear of the boat when running dry. like a vacume . other words
prop end of engine should be 1 inch higher then front of boat.
 
you mean try rasing the rear of the motor so it will lift the front. if i raise the engine stand it will probably help push better because the prop is about 4" from the bottom of the boat and that means that the prop is about 12 to 14 in down inside the boat and about 2" away from transom. so if i tilt the engine the prop might hit the transom. still need a bigger hull.
 
to go trail riding and to go hunting out in the marsh sometimes we run alot of dry ground to get to different places.
 
Not sure there is a perfect combination of top speed and dry ground ability. They require different set ups - same as hill climber jeeps do from strait flat ground top speed cars. If your boat runs trails and dry ground well, then it fits most of your needs. I have found many boats with hooks that are constantly put on rough dry ground due to the licking they take on the ass end. And, plenty of top end rockets that won't climb the hill or dikes at all.
 
might try a 3 blade prop and see how it runs.A buddy just put one on the same setup that I have.We had the same prop and he switched so i'm going to try his boat out and see if it is relly better or not
 
raise prop end of motor lowers nose of boat lower prop end of motor
raises nose of boat. sounds like it would work the other way but it
doesn't. see its not the wind thats pushes the boat. its the prop cutting
thru the air just like a prop does in water. a slightghtly higher rear
will lift the rear of the boat like a vacume. again it is not the wind that
the prop produces that pushes the boat its the cutting of the air like water
that moves the boat.
 
still don't have much room between the prop and transome and still want a bigger hull I was told that a bigger hull would plane better, run dry better,and handle better. You can only put so much in a 11ft 8 in hull I have a 350 ,rotator, and a turbo warp drive that is double stack so the prop is twice the with as a regular warp drive.
 
CCH,

I think you were at Melbourne for the FAA meeting and ride. Maybe not. Anyhow, I was on a friend's boat there. It is a 15' Freedomcraft that's 8' wide with poly. 350 / reduction gear with a Powershift Maximus. I continue to be very impressed as most of my running has always been aircraft powered hunt boats.
The other boat there that raised eyebrows was Greg Abbott's 14' Hoffmann Rivermaster direct drive 472 Caddilac.
Both ran the hill and dry trails there without hesitation and both handled the deep water canals better than most of the others.
My preference would be the 14' Rivermaster. Very Impressive, even with poly and SS rigging.
 
Big Daddy - Have to ask a few questions on that 350.
Is Freedom Craft a fiberglass hull and is he using a 2 or three blade maximus? Do you have any idea what it will turn when wide open?

That is alot of blade to turn with a 350 either way and a big boat.
 
Yes I was out there for the faa trail ride I had the boat with the 350 and no mufflers out there and I was impressed with that 14 ft boat as well. he ran every where with no problem
 
from what ive read, you like runnin the ground more than deep water. i agree the rivermaster is a dang good hull, i run a 12 one now. the problem is fiberglass gets beat to heck and scratched. if i were you id look for a aluminum hull, around 13' or so. as for as the prop goes, youd be a WHOLE lot happier with a wide blade composite prop. its my opinion that the power shift is a better prop for auto motors and sensenich for aircraft. have you looked at hamant hulls in melbourne? they make a great alum. hull and i know quite a few people with them, auto and aircraft.
 
I have a gso 480 with a gear box and log books that I want to sell to get a 14 ft alum might trade for one but going to try to sell it first
 
MarshMaster,

The 15' Freedomcraft has a moderate 350 with aluminum heads. not a sprint car motor. His peak torque point is 4,700 RPM and his two blade Maximus is set to turn 2600 (I think). The prop RPM is what Powershift suggested as max before cavitation. The engine RPM is set for power and longevity and this combo works.

The owner is not completely thrilled with boat fit and finish. The walk around rod boxes are not as strong as Rivermasters' and they have already broken loose down at the hull.

However, this boat will run alongside my 13' fiberglass / 0-540 hunt boat most places. It is no thrill to push & pull when stuck, but is a real pleasure in deep rough waters. Compromise.
 
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