20 hp

What Size Outboard Do I Need For A 15 Foot Boat? Motor HP Boat length (feet) Boat length (metres) 5hp – 15hp 8′ – 14′ up to 4.2m 9hp – 20hp 11′ – 16′ up to 4.5m 20hp – 40hp 13′ – 18′ up to 5.0m 40hp – 75hp 14′ – 20′ up to 5.5m