Supersport Fall off Pad

[SuperSport]

I have tried a number of Props to increase speed and most of the time when I get above ~94 MPH the boat wants to fall off to the right. I am really fighting it and I hate to fight the boat at 94.

Isn't there a "general" rule of thumb saying that when a prop is pushing the boat such that it falls to the right, then the engine height is too high? Or, is it to the left?

I am "trying" to run a Supersport, 260 HP, 28p, Yamaha Drag w/ Hackney cut, running even with the pad, and 12" setback.

Thanks for any help you guys can give.

[racerx]

Put a smaller prop on it till you learn to drive it, such as a 24 when the boat leans over just jerk the wheel back the other way ,that should straighten it out.

[Ray Neudecker]

Falls o the right,need more trim or height.

[On Tap]

Are you talking about an Allison SuperSport?

[props4u2]

I have found that set back of 8" is all the ss needs, have tried 10" set back with same results as 8", 12" may be too much unless you are running a lot of weight foward. Drop the motor to 1/4 to 3/8" below the pad, you will see a big difference in handling, including not lifting the rear left corner, been there done that, not fun. Everyone I know of that has had handling problems with the ss was caused by excessive engine height, someone also mentioned a lower pitch prop to learn with, this is a great idea, just be careful of hitting the rev limiter hard which will knock the boat off the pad.

Lee

[SuperSport]

Thank you, I know how to drive. I've been driving Allisons over 5 years and had a GrandSport over 100. I just don't have the time to play with lots of props, try every engine height and setback. I just wanted to know in which in direction to go.

I do appreciate the last post. I understand that 12" setback may be a little tough on the handling, but I certainly don't have to worry over bow lift props. I am just trying to eliminate variables.

It seems that when I really trim it out, it "kites" pretty bad. I did get a chance to lower the engine about 1/8" (now 1/8 below pad) and I think it helped a bit.

Let's see....huh.....the farther the setback, the lower you need the engine. Or, is it the opposite? In other words, if a person ran 8 to 10 setback and even with the pad; and I am running 12' should I be lower?

I appreciate any thoughts.

[JR IN JAX]

I am also a Grandsport pilot, but I have a little time in a ss over 100 [geat hull, but noisy from the wind]. When you increase the setback you are able to raise the engine slightly more. Usually the ss don't need that much setback [like a Grandsport] if they have adequate power. The hull is much narrower / deeper than a Grandsport so it seems to wobble side to side more often. It's much more stable above 100 than the GS and doesn't move [as much] around in the wind.
Enjoy your toy,
JR

[msethsmile]

general rule I heard--for every 1 inch additional setback the water travels up 1/8 inch. prop must be higher to remain same depth in water. Be careful of teeter-totter effect and 'plowing' the gearcase (which increases the farther back you go).

[Corona Mike]

Are you running a 15"or 20" motor?If you are running a 15"you are really 14"off the transom due to the spacer built into the swivell bracket.This means you are about 4-5" to far off-set.I like running the motor a little higher than the bottom of the boat,but I have a xr2002--totally different boat.The above post is correct,the boat will be easier to drive with a smaller pitch prop.maybe with a little less lift.Good Luck,Be Safe!Mike T.

[props4u2]

The statement that was made about raising motor as you add set back is correct to a point, but with the Allisons this does not apply. With most boats that make a deep hole in the water, when the water comes off of the back of the pad it heads back up to the surface at a high rate of speed allowing you to raise the motor as you add set back, normally 1/4" up for every 1" back. With the Allison, the pad is at the surface, it doesn't matter if you have 6" or 12" of set back, you still run the same engine height.
You stated that it helped the handling dropping it to an 1/8" below, drop it another 1/8 to 1/4" and you'll be there.

Lee

[SuperSport]

Thanks for all your help. I am running 15" offshore and I did include that in my 12" setback calculation. I believe I'll try going lower about 1/4". That will put me 3/8" below the pad.

Thanks again - maybe I'll finally get to the Holy Grail of speed.

[Corona Mike]

SuperSport,If lowering motor doesn't help,try going higher.When I read where your boat was getting "flighty"when you trim it,I rembered mine did that when the motor was to low.Makes since with the motor higher,it takes less trim to lift the nose.Where are you located?If you were in Fla.there is a get-to-gether next weekend on the Alligator chain in St.Cloud and one of the guys putting it on is excellent with Super Sports.Hope info helpa and,like allways,Be Safe.Mike T.

[Yamaha 225]

I had the same problem, but after setting the motor 1" offset to the port side of boat, it disappeared!! If you propride in that speed, you have a problem with your life one day...

Drill some new holes and go out on the sea again!!

[Cp]

Originally posted by Yamaha 225
I had the same problem, but after setting the motor 1" offset to the port side of boat, it disappeared!!

WOW! I never thought of that one. I've seen badly rigged boats with that scenario, but never purposely rigged that way.

Seriously though, tell me you don't have your motor off-center by an inch on an Allison Supersport? Please. This is not the right solution to any handling problem with any boat. If you were worried before that you were going to hurt yourself, I'd start worrying more now.

[props4u2]

Have another thought, do you have a blow out ring on your lower unit? The ring not only keeps the exhaust from wraping arround, it also makes it so you have to use more trim, with the set back you have you are probably running at a negitive trim, at 100 MPH this and the exhaust gas combined will cause the prop to turn loose and drop the boat off the pad. Mercury & Allison have blow out rings you can add on to your unit.

Lee