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PLdrive
05-14-2001, 10:20 PM
I have a few questions and a few observations for you guys running in the upper 90s and above on a 2003 hull. I have a grand sport with a 280 long shaft (stock sport master). Motor is just broken in and I am still getting used to the 280(previous motor 225 pro max).

Conditions
Winds 2 to 3mph, water smooth

Back Ground
Prop shaft is a 1/4 inch of above the pad. Prop is a 28 chopper II (stock) set back 10 or 11 inches (can’t remember, I am on the road this week)
First 3 runs right at 100mph (7400 to 7500RPM) no GPS
Sent prop to Tim Hackney (Allison cut)
Second 3 runs??? (Not sure needle is past 100mph, I’m guessing 102 103 (7300RPM) I KNOW rmps dropped. Tim is going to make some adjustments to bring RPMs up.) Prop is quicker and faster then stock chopper II on my boat. Comes out of the water mush quicker.

Now here is what I am seeing. O to 95 boat runs straight, fairly easy to drive. But as it get s closer to 100 things start to change (both props); Boat does not want to stay on pad (falls to left and to right, very difficult to balance), I have made very small adjustments in weight (side to side) to no avail. I am beginning to think the gear case is developing enough lift to raise the rear of the boat enough to cause the adverse handling. I am planning to raise the motor up to see if handling improves.

Have any of you experienced this? I will post at a few other places as well.

Thanks guys for the help!


Mark

Hank W
05-14-2001, 10:55 PM
Mark,
I'm sorry,I can't answer your question from my own experience but I read that John Tiger(formerly???of Hot Boat magazine?)said the 2003 is a little difficult to drive at near 100 and above by yourself. I just have a 200Promax and have not seen 90 yet. What were you running with a 225?

PLdrive
05-16-2001, 06:19 PM
Hank,
I ran 30 chopper II (et cut) 6750rpm at 1/4 above pad (Sportmaster gear case). 95mph average, saw 97mph once. I gained about 3 mph going from 1/2 below to 1/4 above. I weigh 165 and used 75 pounds of led shot as ballast.

Mark

WillyT
05-17-2001, 08:11 AM
I have heard from a couple of sources that the Grand Sport is the hardest Allison to drive at the 100mph+ levels (real nice boat, though!) Even the Allison bass boats that are capable of these speeds are easier to keep on pad. I wonder if a set of transom-mounted afterplanes, mounted flush/inline with the Vee part of the bottom on each side of the engine would work? I know that the Land and Sea catalog used to sell turnbuckle-adjustable ones, and they said that speed was actually increased on some light/fast V bottom boats due to the added tail lift that resulted (in addition to the elimination of chine-walk or other handling problems). On some boats, you literally "run out of bottom" after a certain speed, and there is nothing left to hold the boat up. Afterplanes are like adding a "extra/longer/wider" bottom. Anyone ever tried them on an Allison? Are these ever seen these days on drag boats for better hole shot, or is everyone just using "whale tails" for hole shot? I guess if you tried them and they didn't work, you could just angle them up a little and get them out of the way of the water at high speed (would still help some with hole shot). Just a thought.

Hank W
05-18-2001, 08:43 AM
I haven't ever tried planes. I would need more HP before I would try them. I haven't approached 100mph as I said before, but at speeds near 80mph, I can assure you that the GranSport is more difficult to drive than my Hydrostream Viper. Funny though,I think the Allison is the preferred boat? The 'Stream feels more "dangerous"(loose) at these speeds but I can almost drive it w/one hand. The GranSport will definitely take the rough stuff more predictably. Of course it is 5 feet longer and around 400# heavier. Anyone else have a similar comparison or experience?