Adam,
It is a small world! Your right hand props have a small diameter hub. They appear to be more like a Mercury "quicky" lower unit diameter. What is your engine and lower unit ? This Columbian is a solid hub with a bronze/brass insert for a 3/4" shaft. The front edge diameter is 2 7/8". It was made for the standard shifting outboard lower units I think. Are you going to Clayton this summer?
