What is the minimum allowed clearance between the propeller blade tips and hull bottom? How much space should exist between the propeller and strut or keel?
The clearance between the propeller blade tips and the hull bottom should be at least 15% of the propeller diameter and ideally, 20% or more. So for example, a 20″ diameter propeller would have 3″ minimum clearance and better still 4″ or more. A common guideline for recommended propeller to strut or keel clearance is 20% of propeller diameter measured between the propeller blade edge and strut leg or keel. This is often measured at a point on the propeller blade edge about 70% of the distance from the shaft centerline to the blade tip.
