A stern thruster mounts in a tunnel or an external pod at the transom and works with your bow thruster so you can move the whole boat sideways or spin it in place. It is the single biggest docking upgrade for single-engine boats and boats with lots of windage. We size it to pair with your bow unit.
Why add a stern thruster
With a bow thruster alone you control the bow, and the stern is still at the mercy of the wind and your engine. A stern thruster lets you push both ends at once. Hold both joysticks the same way and the boat slides sideways. Push them opposite ways and she spins on her center.
It matters most on single-engine boats, boats with a lot of windage aft (flybridges, tall sterns), and owners who dock short-handed.
Tunnel or external?
If there is room for a tunnel at the stern, it is the cleanest option. On many boats there is not, because the running gear, the swim platform or the hull shape gets in the way. That is where external stern thrusters come in: the unit mounts on the transom below the waterline, with the motor inside. No tunnel, less glasswork, and often a shorter install. See tunnel vs retractable vs external and our external stern thruster review.
Pairing with the bow unit
The stern unit is usually sized close to the bow unit and run from the same control panel or joystick. If you already have a bow thruster, we check its age, voltage and control system so the two work together, and plan power for both. That usually means a second dedicated battery aft or a properly sized cable from the bow battery.
What the install involves
For a tunnel unit the steps mirror a bow install. For an external unit, we bore through the transom, bed and backing-plate the mount, then wire, fuse and test. Many external installs finish in one to two days.
Questions people ask
Do I need a bow thruster before adding a stern thruster?
In practice yes. A stern thruster on its own is unusual; the payoff comes from controlling both ends. If you are starting from scratch we usually quote bow and stern together, which saves a second haul-out.
Can I use a joystick with bow and stern thrusters?
Yes. Most makers offer a single joystick or combined panel that drives both units. Proportional systems give you finer control. Compare with full engine joystick systems in our joystick docking review.