Davis Rudder Position Indicator 
Rudder Position Indicator
Awareness of the rudder angle is an important safety factor. This is especially true while moving in and out of your berth, drawing alongside another boat, picking up a skier, mooring, or any other "close call" situation. Davis' Rudder Position Indicator gives instant visual reference of rudder angle.
The pointer swings a full thirty degrees with each revolution of the wheel. Mounts directly to your hub (approximately 2" (5 cm) in diameter) with a self-adhesive pad . Rugged, hermetically sealed, weatherproof, and sunproof housing ensures long life. No cables, adjustments, or electricity required; gravity power makes it simple and service-free. Suitable for boats with mechanical and single station hydraulic steering systems.
Owner's Manual (pdf)