Gregg, very interesting. I am surprised that the flat bottom Challenger only went 51.7 MPH when the hull was 490 lbs. The Mercury is a 15" short shaft raised on the transom 1 7/8". My V-153 hull weight 630 pounds with a 115 HP Merc goes 52.9 MPH GPS.
In my opinion, the Carlson Challenger would have gone faster if they had done two things. (1) Use power trim which they did not have back then. (2) Used a different prop. They were using a 2-blade 23" bronze prop with a 13 3/4" diameter to be used with a maximum weight of 1,000 lb. Their weight was 1,338. The RPM's must have been below redline, my guess around 5,000.
They should have dropped to a 2-blade bronze 13 3/4" diameter, 21" pitch cupped. That would have brought their RPM's up closer to the redline of, I would guess, 5,300 RPM.
Their may be alot of other factors, such as temperature, lower unit and engine oils are better now, closer tolerances in the engine, etc.
Hey, but that was 1964, 47 years ago.
