Besides what Hartmut said, a heavy Coupe with a cruise prop (7151 or 7152) may not be able to get up to cruising speed due to load and insufficient horsepower to turn that pitch of prop adequately.
While a 1260 pound Coupe might cruise 112 mph with a 7152 prop, a 1400 pound Coupe may only cruise at 90 mph at near full power with the same prop. So, if you want the fast cruise, either you need the horsepower to do it or a plane light enough to do it with the engine/prop you have. Each airframe, just like each boat/ship hull, has a range of speed it can reach with moderate power. Past that speed, the power requirements go up steeply. Ercoupes and Forneys get to that elbow in the graph somewhere around 110 mph. The guy who mounted a 135 horsepower engine didn't go much faster than that - he just got humongous climb and fuel consumption (and a very ugly plane). Mark in Wisconsin (who used to work for a previous owner of Skyport and who designed the 30 gallon fuel tank system) is one of the few who has made a higher power installation effective and he really worked at it intelligently. Me, I was happiest with my C-85 engine and a 7146 prop that gave me adequate climb even though my 2400 rpm cruise speed was only 100 mph. Ed
