Are you saying you have a boat that measures 20" from top centerline of transom to bottom of boat hull and want to know what shaft length engine to mount??
The better measurement is from the top of the transom, vertical to a point even with the bottom.<br /><br />You should use an outboard that measures the same from the surface that sits on the transom edge to the anti-ventilation plate.<br /><br />Good luck.
