motor questions for newbie

[X-1hydro]

whats the speed on your hydros? should i expect more or less of what your runnin? also on the turn fins how would i go about that just one in the center or what? this is new to me so im kinda lost on a lot of things here. my dad kinda helps but this hydro is a lot more to the 8 foot cab-over he built way back. and what modifications will i have to make. if need be i can show you all the plans and any info you need to know. again any help is helpful and i thank all who have helped thus far.

[Winger Ed.]

whats the speed on your hydros?

The speeds I'm getting are much, much lower than similar boats built for competition. Plus, I weigh about 100 pounds more than the average driver who expects to have a chance at winning one of these races also.


The yellow 'D' with the stock 50hp Merc on it as well as the 16'er are totally foamed solid. That darn near doubles the weight of the hulls compared to ones built to race.

With me in the 'D', at 260 pounds, it does about 50 mph or a little better with a 16' pitch prop at 4,500-odd rpm. A similar, lighter weight hull with a smaller driver will probably do closer to 80 as the engine could wind up higher.

The white one with the (almost) stock 150, a 26" Chopper prop., and me in it does almost 90 at about 65-6,700 rpm or so. The foam in it adds about 200 pounds to the weight of the hull, and I carry a 16 gallon fuel cell. With someone weighing about 150 pounds, carrying less gas, it should easily get up to 100mph on flat water.

Your turn fin should normally be made from 1/8th inch Alum. plate.
I bring mine down off the inside edge of the rear ends of the sponsons. If you put one under the centerline, it will have to attach like a "T" along the keel. The fin/air traps you see on the yellow D are the same on both sides. They help trap more air under the hull and give it a little more lift to come up out of the water a little higher than just a turn fin alone**.

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Keep in mind, these are 'ground effect' vehicles (that is the big surge upwards you feel just as a airplane is a few feet off the runway on landing.. You're coming down, then right over the ground you feel a big push up as air is compressed between the ground and the bottom of the wings). The top of the hull is an airfoil- like a airplane wing- that generates lift, as well the tunnel under it compresses air underneath- pushing the hull up. Since air resistance is easier to go through than water resistance,,,, The idea is to get as much of the hull up & out of the water as possible.
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