The top of the tunnel must sit at least 1x the tunnel diameter below the waterline to prevent sucking air (cavitation).

Dedicated thruster batteries should sit close to the motor to minimize voltage drop.

To ensure the safety of your vessel, always disconnect the main thruster batteries before working on any electrical connections or mechanical components inside the bow compartment. If you need help identifying a specific component, tell me: What is the (12V or 24V)?

Need a specific diagram or wiring schematic? Please provide the exact model number from your unit's nameplate.

Boat maneuverability relies heavily on dependable thruster systems. Quality Line (QL), a brand historically associated with Volvo Penta, manufactured highly efficient mechanical and electrical bow thrusters. While many of these units are now legacy systems, thousands remain active in marine vessels worldwide.

The QL series features compact, high-torque electric DC motors connected to a submerged propeller via a streamlined gear leg. These units operate on either 12V or 24V DC systems, depending on the specific model (such as the popular QL BP300, BP600, or BP800 series). Core Components

1. Propeller shear pin broken.2. Propeller missing.3. Tunnel heavily fouled.

Located inside the hull; provides high-power, short-duration thrust.