Mark75H
07-22-2002, 09:41 AM
Just before they became McCulloch, Scott had a racing program.
The std 63ci motor was converted from 60hp to 88hp by replacing the internal reed valves with an external rotary valve, bigger carbs and a head that changed the combustion chamber from a very bad wedge shape to an almost perfect hemi shape. The standard 1/8 (.125) thick rings were replaced with rings about .030 thick.
A short mid section lowered the motor a little. The bottom end was finished off with a true racing lower unit. This lower unit had a few features that made it better than the competition.
1) the gears had very fat teeth, made as if they were going to be bigger, then reducing the diameter.
2) pinion/prop shaft gear ratio was not 1:1, but one tooth off. This greatly improved the life of the gears. Gears would last over 40 hours at 80mph, more than 5 times better than a Speedmaster of the same era.
3) actual drive ratio was selectible by changing "quickchange" gears above the lower unit. Several pairs of reversible gears gave ratios from 2:1 reduction to 1:1 to the reciprocal overdrive ratios. Took about 45 minutes to change, no shimming or setting required.
5) above the prop shaft the unit is FAT. Who cares what it looks like, its functional and..... who drags that part underwater anyway on a race boat?
6) a large skeg for good steering
Props were made by Warren Litton
The races mentioned in this ad were sanctioned by WOA, not APBA: Lake Havasu-Site Six 100 miles, Big Bend, Carlsbad, Pine Flats, Lake Casitas, Mission Bay, Green River (196 miles)and Lake Mead
The std 63ci motor was converted from 60hp to 88hp by replacing the internal reed valves with an external rotary valve, bigger carbs and a head that changed the combustion chamber from a very bad wedge shape to an almost perfect hemi shape. The standard 1/8 (.125) thick rings were replaced with rings about .030 thick.
A short mid section lowered the motor a little. The bottom end was finished off with a true racing lower unit. This lower unit had a few features that made it better than the competition.
1) the gears had very fat teeth, made as if they were going to be bigger, then reducing the diameter.
2) pinion/prop shaft gear ratio was not 1:1, but one tooth off. This greatly improved the life of the gears. Gears would last over 40 hours at 80mph, more than 5 times better than a Speedmaster of the same era.
3) actual drive ratio was selectible by changing "quickchange" gears above the lower unit. Several pairs of reversible gears gave ratios from 2:1 reduction to 1:1 to the reciprocal overdrive ratios. Took about 45 minutes to change, no shimming or setting required.
5) above the prop shaft the unit is FAT. Who cares what it looks like, its functional and..... who drags that part underwater anyway on a race boat?
6) a large skeg for good steering
Props were made by Warren Litton
The races mentioned in this ad were sanctioned by WOA, not APBA: Lake Havasu-Site Six 100 miles, Big Bend, Carlsbad, Pine Flats, Lake Casitas, Mission Bay, Green River (196 miles)and Lake Mead