Bow Thruster Installation: What Size of Sleipner Thruster Do You Need?

So, mooring in your marina can be a bit of a nightmare, particularly in windy weather or at busier times. You’ve heard that a bow or stern thruster can help. At JPC Direct, we stock, install, service and support Sleipner thrusters, which are widely accepted to be some of the best available on the market. But what size will you need?

Generally speaking, any thruster will do some sort of job in any boat. The key, though, is to ensure that your chosen thruster will do the most economical and efficient job for your boat and your individual requirements.

This is one of two main factors in choosing the correct size of thruster for your boat.

Nowadays, most pleasure craft over 35′ have a bow thruster fitted as standard, which will usually do a job in “normal” weather conditions.

The sizes used by boat builders will vary depending on the boat’s intended usage and price level.

In today’s production boats, the typical thruster will push the boat’s bow against a direct side wind of 24-26 knots.

Sizing example for a Sleipner thruster

If you have a 45’/13.5m boat, you have four tunnel thrusters to choose from within “normal” sizing.

If your boat does not have a lot of wind area and you use it mostly in good weather conditions, you can choose the least powerful thruster, the SE80, in a 185mm tunnel.

If you want to keep the 185mm tunnel diameter, but require more power, the SE100 would be a good choice.

If you have room for a larger tunnel diameter, there are models in both 215mm and 250mm tunnels for this size of boat.

NB – Generally speaking, a larger tunnel diameter will be more energy efficient and generate less noise.

Key factors in sizing a Sleipner thruster

• The boat owner’s performance requirements
• Boat size, type and shape

Example guidelines for tunnel thrusters*

*Please note that the sizes in the graph above will also apply for retractable thrusters and for external “pod” type bow and stern thrusters.

Choosing a stern thruster

A stern thruster does not require more thrust to give the same effect as a bow thruster.

The reason for this is that the stern thruster is mounted outside the hull, further from the boat’s pivot point, and generates much more leverage.

Depending on the boat type and wind area of the boat, the same size or the size below will be a good match for your bow thruster, given that you have the right-sized bow thruster in place to start with!

Do remember, though, that if there are any obstacles in the water flow to and from the stern thruster, then a larger model may be required.