It looks like you have it nailed down very well. A standard gearcase is built for general service. Some owners use them to dig channels in shallow anchorages. Manufacturers keep this in mind when designing service lower units. They go even farther for special work motors. The heavy duty gearcase on the old Light Four has a 3 to 1 reduction and swings a 13" diameter propeller. The Army storm Bout Motor had wings to protect the propeller when running up on enemy beaches. Racing lower until are designed for the least drag. Big and rugged is a distinct disadvantage where speed is the major concern.
Here is the HD gearcase used on the storm boat Motor
and the gearcase for the racing 460 –
When the OMC V4 was designed in the mid ’50s, It was thought it would replace twin motors on a big heavy boat. It was built heavy and rugged. People were shocked that it burned gas like two motors. People wanted speed and econimy. Engineering immediately went to work on impovements. It was found in took 40 horse power to push that football gearcase through the water at 40 MPH. The slimmer gearcase on the 1960 V4 only takes ten HP, leaving 65 horses to push the boat.
