As part of the owner’s retirement plan, this early-2000s Elan 40 underwent several important upgrades, including a new engine and the installation of a bow thruster. What follows is a step-by-step overview of the installation process, excluding electrical work and wiring, for those considering a similar project on their own boat.

To be on the safe side, allow at least a week for this small “half-hour” project.

Before starting, make sure to protect the environment, the people and boats around you, and the interior of your own boat from sticky fiberglass dust. And, of course, protect yourself properly as well.

Choosing the right bow thruster begins with a preliminary inspection of the forepeak to understand the available space. From there, you need to determine the correct unit in terms of power, thrust, tunnel diameter, overall dimensions, and cost.

To work out the position of the thruster, a simple cardboard side-view template of the motor unit can be very helpful. The main considerations are fitting the unit under the bunk and placing the tunnel as low as possible. A useful rule of thumb is that the upper edge of the tunnel should sit at least one tunnel diameter below the waterline.

The next step is finding the center point of the tunnel. Neodymium magnets can be used to transfer this point to the outside of the hull. Then check the position by measuring from the freeboard and from the bow to confirm that both sides are correct and symmetrical.

A piece of metal shaft works well as an axis for marking out the holes.

The holes themselves are easy to cut with a jigsaw.

After that, bevel the hull properly around the openings for laminating the tunnel into place.

For the initial bonding, Sikaflex can be used to secure the tunnel to the bulkhead in the middle, while epoxy mixed with microballoons and silica filler can be used to bond the tunnel to the hull.

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The “ears” are optional, but if needed, they can be shaped with an epoxy compound mixed with microballoons and silica.

Laminating the lower part of the tunnel to the hull is, as always, the most “entertaining” part of the job – use epoxy and small pieces of roving to build up a strong, reliable bond.

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A cardboard template can again be used to mark the opening for the bow thruster motor unit.

Finishing the outer surfaces takes some sanding, fairing with polyester filler, followed by epoxy primer and antifouling.

Then comes the moment to take a deep breath and drill the holes in the tunnel for the motor unit. After that, the inside surfaces can be finished and the motor unit installed permanently.

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If the motor unit is installed at an angle of more than 30 degrees, it will normally require additional support. It is a good idea to place a rubber pad or some Sikaflex between the support and the unit to help reduce vibration and noise.

Installing a bow thruster is a mid-level complexity project, requiring a certain level of fiberglass, electrical, mechanical and project management skills. Professional advice is recommended.