As harbors become more crowded and boats are getting bigger it becomes more difficult to maneuver safely and accidents are likely to increase. A thruster makes docking easier and safer, because it gives the captain more control over the boat and makes a ship or boat more maneuverable. With the right bow or stern thruster installed it is possible to turn the vessel to port or starboard without using the main drive.

When choosing the right thruster for your boat it is important to consider a few basic guidelines by asking yourself the following questions.

• What’s better, a bow or stern thruster?
• What kind of thruster is best for my boat?
• How much money do I want to spend for a thruster?
• How long will it take to install a thruster?
• How much space do I need in the boat interior to install a thruster?
• What is the maximum runtime of the thruster?
• How efficient is the thruster?
• What about the noise, how loud is the thruster?
• What kind of warranty comes with the thruster?
• How easy or complicated is it to repair the thruster if it needs to fixed?

What’s better, a bow or stern thruster?

This is the first thing you should decide as this will further impact the price and installation of the thruster. If you only want to install one thruster and space is not an issue, you should decide on a bow thruster, given that your main drive is at stern. A bow thruster will provide you better control and maneuverability and is more efficient than at stern. Unless you have a very large yacht or a houseboat one thruster at the bow is enough. If you own a houseboat a second thruster installed at the stern is sure nice to have. The added control provided by a stern thruster helps you to avoid accidents while docking.

What kind of thruster is best for my boat?

There are two main differences when it comes to thruster besides bow versus stern thruster. You can get a tunnel thruster or an externally mounted thruster.

Tunnel thruster:

When you buy a brand new boat and you have the choice over a tunnel thruster opposed to an externally mounted thruster, the tunnel thruster is definitely the way to go.

A tunnel thruster is usually built into the bow below the waterline. The tunnel position in the boat is important. The further forward you install the tunnel, the more leverage. Most tunnel thrusters are like external mounted thruster driven by electric motors, for bigger boats they are also available hydraulically powered. An impeller in the tunnel can create thrust in either direction which makes the boat turn.

Disadvantages of tunnel thrusters:

• Because a tunnel thruster increases the vessel’s resistance in the water it can slow the boat down and use more gasoline.
• The tunnel can also weaken the hull of the boat and therefore damage the hull easier than a vessel without a tunnel thruster installed.
• Fouling of tunnel and impeller is another issue to consider when making your choice for the right thruster. It is important to protect the tunnel either with protective grate or by cleaning.

Externally mounted thruster:

External thrusters are great to retrofit or where space is limited inside the boat. Because the current doesn’t stall directly along the hull and therefore generates less turbulence, an externally mounted thruster slows the boat less than a conventional thruster with transverse tunnel. You can also position an external thruster deeper which causes less ventilation and prevents vortexing due to wave movement, giving you better efficiency.

Depending on the type of the external thruster you can install it either at the bow or stern.

How much money do I want to spend for a thruster?

To find out how much money you are willing to spend for a thruster you should think about how often you will use the thruster. As with everything, quality has its price.

If you only use the thruster once every few months you can find a fairly cheep external thruster.

If you’re planning to use the thruster more frequently and for longer periods of time (see runtime of thruster) you should invest into a professional solution that works even under extreme conditions.

How long will it take to install a thruster?

Generally, either type of thruster can’t be installed while the vessel is in the water, more times than not it will have to be dry docked.

Adding a tunnel thruster to an existing vessel requires cutting tunnel openings in the hull plating and longitudinal bulkhead (if any). Depending on the hull material the thruster tunnel must be weld into the hull. The installation of an external thruster depends on the thruster type, but is usually far less time consuming and can be achieved in a day. It also requires no drying period of thermosetting plastics.

How much space do I need in the boat interior to install a thruster?

Conventional tunnel thrusters need space inside the boat for the motor and gear. Externally mounted thrusters do not require any space inside the boat and only need a cable to the battery.

What is the maximum runtime of the thruster?

Since all electric motors create heat as a byproduct during operation, the runtime depends on the cooling capacity of the motor. Because the motor of an external thruster is emerged in the water the cooling and therefore runtime is far better than a tunnel thruster of the same power class.

How efficient is the thruster?

If it is possible to position a tunnel thruster perfect below the water line and avoid vortexing, the efficiency, to a comparable external thruster is about the same.

Because an external thruster can be positioned deeper, less ventilation and vortexing due to wave movement, results in better efficiency.

What about the noise, how loud is the thruster?

Since the motor of an external thruster is emerged in the water and not in the inside of the boat like the motor of a tunnel thruster, the noise of a is far less.

What kind of warranty comes with the thruster?

Warranty is obviously a very important criterion when choosing a thruster for your boat. Make sure your thruster has at least a 2 year warranty.

How easy or complicated is it to repair the thruster if it needs to be fixed?

Make sure you can get replacement parts if something breaks. Even though there are many maintenance free thruster available make sure it is easy to replace parts if needed without major modifications.