Summary
Bow thrusters buying guide
Welcome to our "How to choose and use a bow thruster" guide. Bow thrusters are a useful piece of equipment for maneuvering a boat. Installed at the bow, they generate lateral thrust to move the vessel sideways or diagonally.
Comprising a motor, propeller and hull tunnel, they are easy to control from the cockpit. Bow thrusters are ideal for maneuvering in harbor or tight spaces. They improve the boat's maneuverability at low speeds and reduce the risk of damage or collision.
The choice of thruster depends on boat size, sailing conditions and personal preference. Our guide will help you understand and use these devices effectively.
Bow thrusters buying guide
Welcome to our "How to choose and use a bow thruster" guide. Bow thrusters are a useful piece of equipment for maneuvering a boat. Installed at the bow, they generate lateral thrust to move the vessel sideways or diagonally.
Comprising a motor, propeller and hull tunnel, they are easy to control from the cockpit. Bow thrusters are ideal for maneuvering in harbor or tight spaces. They improve the boat's maneuverability at low speeds and reduce the risk of damage or collision.
The choice of thruster depends on boat size, sailing conditions and personal preference. Our guide will help you understand and use these devices effectively.
What is a bow thruster?
A bow thruster is a device installed at the bow of a boat (yacht, sailboat, pleasure boat...), below the waterline on the sides of the hull. It's a motor with a propeller that moves the boat sideways or diagonally. This helps sailors to maneuver more easily, especially when entering or leaving harbors or moving in tight spaces.
The bow thruster consists of a motor, a propeller and a tunnel integrated into the boat's hull. The motor turns the propeller, creating a powerful flow of water that pushes the boat in the desired direction, enabling the sailor to move it with greater control and precision.
The advantage of having a bow thruster is that it facilitates tricky maneuvers at low speeds. For example, when trying to enter a boat parking space, or when you need to turn quickly in a restricted area. The bow thruster reduces the risk of collision with other vessels or docks.
Different types of thrusters
First, let's talk about the bow thruster. A bow thruster is located at the front of the boat (bow) and pushes the bow to the right or left (starboard or port). It can be electric or hydraulic. But there are also stern thrusters, which are located at the stern and also help the boat maneuver.
There are 4 main types of bow thrusters:
Thruster type |
Description |
For what type of boat? |
|---|---|---|
| Retractable bow thruster | This type of thruster can be retracted inside the boat's hull when not in use. | Medium to large pleasure boats, yachts |
| Fixed tunnel bow thruster | The thruster is integrated into a fixed tunnel in the boat's hull, and remains in place at all times. | Medium to large pleasure boats |
| External bow thruster | This type of thruster is installed on the outside of the boat's hull in a fixed watertight block. | Pleasure boats, sailboats, motorboats |
| Water-jet bow thruster | Instead of a propeller, this type of thruster uses a jet of water to generate the propulsive force. | Fast boats, service vessels |
There are also variants such as retractable steerable thrusters, where the propeller can be steered to direct the flow of water in different directions. Or the twin-screw bow thruster, which uses two propellers for more powerful lateral thrust.
To simplify the purchase of a tunnel bow thruster, we've put together ready-to-install kits comprising an electric bow thruster for sailboats or motorboats, a tunnel, a joystick control panel, a control cable, a circuit breaker, a fuse holder, a fuse and a battery. Discover our all-in-one thruster kits.
Fixed tunnel bow thruster
For a flexible, adaptable option, the best choice is a well-designed, professionally installed tunnel thruster. Make sure your boat has sufficient internal space and adequate access to the bow for proper installation. The position of the submerged tunnel in relation to the waterline is important for optimum performance and noise reduction.
Today's tunnel thrusters offer fantastic functionality. By choosing a reputable manufacturer, you can opt for an advanced system that allows precise control of the thrusters, similar to using the accelerator pedal in a car. This offers total maneuverability in tight spaces and easy one-handed control.
- Wide range of choices available
- Good value for money compared to other options
- Troubleshooting and maintenance can be carried out without lifting the boat.
- No reduction in boat speed when the tunnel is correctly installed.
- Installation requires sufficient interior space in the hull.
- The tunnel must be located at least ½ to 1 times its diameter below the waterline.
- Some noise emission is possible if the tunnel is not optimally installed.
Retractable bow thruster
Retractable thrusters are gaining in popularity and can be installed either forward or aft of the hull. They are particularly suitable for custom yachts and flat-bottomed boats that cannot accommodate a traditional tunnel thruster due to shallow draught. (Height of submerged part of boat)
Retractable thrusters use shorter tunnels housing propellers, making them more efficient and less noisy than traditional tunnel installations. The best retractable thrusters are equipped with grounding protection, and some offer variable speed control.
- Efficient thrust thanks to good depth and short tunnel length
- Often little or no noise
- Requires more interior space than tunnel size
- More vulnerable to damage from external protrusion
External bow thruster
External boat thrusters are a practical option for vessels with limited interior space , or for those wishing to avoid the high cost of installing a retractable thruster or a complete tunnel. They come in a variety of forms, the most common being torpedo-shaped solutions mounted under the hull. These thrusters benefit from a hydrodynamic housing that reduces drag and makes for more economical installation.
However, external thrusters protrude from the hull, which can cause problems if you regularly launch your boat with the aid of a trailer, or if you store it ashore on a raised pile system. In addition, they are not suitable for planing hulls, as they can increase water resistance and the associated drag.
- Easier and quicker to install, perfect for retrofitting
- Greater efficiency thanks to optimal positioning
- Quiet operation in most cases
- Long operating life thanks to efficient water cooling of the motor
- Small footprint on the bow surface
- Some negative effects of increased water resistance and associated drag.
- Care must be taken when removing the hull, re-launching the boat or storing it ashore.
How to choose a bow thruster?
Which thruster for my boat?
Things to consider when investing in a bow thruster
- Boat profile (dunnage): The longer and higher your boat's body, the more the bow thruster has to cope with wind pressure.
- Bow shape and interior space : the deeper the bow is in the water, the greater the interior space, making it easier to install the thruster.
- Capacity : The more wind and current there is where you're sailing/anchoring, the more powerful the bow thruster needs to be.
- Power : small boats generally use DC power, while larger boats use AC or hydraulic power. If your boat is over 60 feet long, check that it is not already equipped with an AC generator or hydraulic system.
- Budget: The size, power and options of the different thrusters available for your boat will vary according to price and installation requirements.
How much power do I need?
Whether you've decided to buy a bow or stern thruster, or are considering upgrading an existing installation, you'll need to determine how much thrust power is required to meet your specific needs.
By definition, any thruster will do the job to some extent. The key is to ensure that your chosen thruster will work as intended in your particular boat, so as not to underestimate or overestimate the power required to move your vessel.
Here is a table to help you select the appropriate thrust of the thruster (in kg) according to the length of your vessel and the dunnage:
| Vessel length | Lightweight dunnage | Medium dunnage | Heavy-duty dunnage |
|---|---|---|---|
| Up to 10 metres | 30 kg | 50 kg | 80 kg |
| 10 - 15 metres | 50 kg | 80 kg | 120 kg |
| 15 - 20 metres | 80 kg | 120 kg | 180 kg |
| 20 - 25 metres | 120 kg | 180 kg | 240 kg |
| 25 - 30 metres | 180 kg | 240 kg | 300 kg |
Please note that the values given are general estimates and may vary according to other factors specific to your boat. We recommend that you consult the thruster manufacturer's specifications.
bow thruster position and installation
As we've seen, the size of the thruster depends on several factors: the dunnage, the wind pressure on the boat and the thrust required to counter this pressure. But proper positioning of the thruster will also optimize its performance.
Tunnel thruster
Where to position my tunnel thruster?
The position of the thruster will depend on the internal and external structure of the vessel. For optimum performance, an internal tunnel thruster should be installed as follows:
- As far forward as possible to maximize leverage (Fig 1)
- 1 x Ø (0.75 x Ø minimum) below the waterline to prevent air being drawn into the tunnel (Fig. 2). Ø= Tunnel diameter
- Minimum recommended tunnel length 2 x Ø.
Tunnel thruster installation
The installation of a tunnel thruster is a technical operation and must be carried out by a professional:
- Preparing the site: Make sure the area where the tunnel will be installed is free of obstructions and clean. Check the dimensions, diameter and precise location of the tunnel in accordance with the manufacturer's recommendations.
- Cutting the hole: Use appropriate tools to cut the hole in the boat's hull, according to the tunnel's diameter. Be sure to follow the manufacturer's instructions for a precise fit.
- Tunnel installation : Carefully place the tunnel in the cut-out hole, ensuring that it is correctly aligned and positioned.
- Waterproofing : Apply a recommended waterproofing material, such as epoxy resin, to the surfaces of the tunnel in contact with the boat's hull. This will ensure watertightness and prevent water infiltration.
- Drilling the tunnel : Drill the tunnel so that you can attach the thruster.
- Thruster installation: Carefully insert the thruster facing the cut-out hole, making sure it's correctly aligned and positioned.
- Electrical connection: Make the necessary electrical connections in accordance with the manufacturer's instructions.
External thruster
External thrusters are much simpler to install, and can be used both as bow thrusters (at the front of the boat) and as stern thrusters (at the rear).
Where to position my external thruster?
Installing an external bow or stern thruster is quick and easy, but it's essential to call in a qualified professional to carry out this operation. For optimum bow performance, the thruster should be mounted as low and as far forward as possible, generally at least 30 cm below the waterline, measured from the center of the propeller.
Similarly, for stern mounting, it's best to place the thruster as low and aft as possible, with a depth of around 30 cm below the waterline. By adhering to these mounting recommendations, the thruster can operate efficiently and contribute to improved boat maneuverability.
There are several possible positions and locations for an external thruster on a motorboat
Bow thruster:
- Front-mounted under the hull just below the waterline
Stern thruster, 3 choices available:
- Classic external rear thruster mounting under the hull
- Mounting the thruster on the rear platform
- Vertical mounting of thruster on transom
On a sailboat , the assembly is classic for an external thruster.
Bow thruster :
- Front-mounted under the hull just below the waterline
Stern thruster :
- External thruster mounting at rear under hull
External thruster installation
Installing an external thruster is simple, but must be done by a professional.
Prepare the site: Clean the installation area and make sure it's smooth.
Mark mounting points: Use the manufacturer's instructions to mark the points where the thruster will be mounted.
Drill the mounting holes: Use a drill to drill the holes where marked.
Installing the thruster: Carefully place the thruster in the drilled holes.
Attach the thruster : Use the screws or bolts supplied to secure the thruster to the hull.
Sealing: Apply a Sika-type sealant to the joints.
Connect the electrical cables: Connect the thruster cables to the boat's electrical system.
Retractable thruster
A retractable bow thruster should be positioned as far forward as possible on the boat. When the thruster is in the deployed position, the tunnel must be clear of the hull and the centerline of the propeller shaft must be below the waterline at a distance equivalent to at least 1.5 times the tunnel diameter.
Retractable thruster installation
Identify the location of the thruster: Locate and trace the opening on the hull.
Cut the opening: Using a jigsaw, cut the opening according to the manufacturer's recommendations.
Fix the counterflange: The counterflange, or support, is inserted into the opening.
Attach the thruster: Align the thruster and secure it in its bracket.
Sealing: Resinate and seal contours with recommended products
Electrical cables: Connect the thruster cables to the boat's electrical system.
