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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

Mark75H
07-22-2002, 09:44 AM
Cut away of the lower unit. Not near as pretty as a Speedmaster, but they weren't made for looks. Sort of Art Deco meets Rube Goldberg vs the seriousness of a torpedo compared to a Speedmaster.

In retrospect Kiekhaeffer and Charlie Alexander may have compromised the Speedmaster's strength a little with the narrowness of the unit above the bullet, but you can't beat it for looks.

Kiekhaefer did have the Quicksilver units cosmetically altered to reduce the obvious bulge of the gears. Anyone here know what that was?

Powercat
07-22-2002, 12:53 PM
One of our PowerCat owners current boat
with the McCullough's on it. Runs in the
mid to high 60's..
Danny Leger

Mark75H
07-22-2002, 03:56 PM
Dick Davis's Powercat is a beauty! His motors are the other OPC McCulloch variation: The Flying Scott "Custom".

These motors are production line 75 hp motors with McCulloch's 1.1:1 full gearshift "Sportsman" lower unit. These are the late type "one piece" units with the 8 1/8" wide cavitation plate----there is nothing else with a plate that wide. Early "Sportsman" lower units had the same full gearshift and 1.1:1 ratio but the housing was 2 pieces bolted together and the rear bearing/seal carrier was different. I suspect the original type unscrewed and made a lot of boaters unhappy. :(

The McCulloch "Custom" series motors were the standard motors on the McCulloch boat-motor-trailer combinations----but could also be ordered separately as could the 1.1:1 ratio F-N-R lower unit.

Most Scott/McCulloch guys just call this lower unit a "Custom", the "Sportsman" name was forgotten about as soon as it was announced.

warrior74z
03-29-2007, 05:54 PM
I remember in the late '60s or early '70s I was just a teenager but remember dad taking in a trade that had one of these engines on it. I want to say the boat was a Scott and it was a fiberglass three point hydro but in a pleasure boat model. I knew it was probably too heavy to go fast but the thing I remember was it had some sort of vertical trim system to vary engine height. It got sold before I got my hands on it but wish I had it now!!
Barron Cooley

Mark75H
03-29-2007, 07:00 PM
Your memory is very good; all those details are correct. :)

They could go over 50 mph, which was pretty respectible back then ... 65 or so with 2 75's

Sunburnt
03-30-2007, 01:13 AM
Yup, it would be considered a treasure today...