Choosing the best bow or stern thruster for your vessel is quite critical, as the thruster probably will accompany your boat for decades to come. In this article, we will share our collective knowledge from more than 40 years of designing and manufacturing thruster systems for leisure and workboats. Our goal is to guide you towards the best possible thruster system for your vessel and your needs. In this article, we will primarily address bow and stern thrusters with 12 and 24 VDC operating voltage.
For AC electric and hydraulic bow thrusters and stern thrusters, please visit our dedicated blog here.
Thrusters are well-established tools that come standard with almost every new boat designed over around 25 feet. But for those who wish to retrofit or upgrade an existing system, the product range of boat thrusters is now far more extensive than just a few years back, so it is important to research thoroughly and understand which solutions will work best for you.
We hope both boat owners, boat brokers, boat manufacturers and other interested parties will find our articles helpful and practically useful!
A boat thruster is a device that moves the boat in a sideways direction. Vessels outfitted with both a stern and bow thruster also have total 360 directional manoeuvrability. The most common type of boat thruster is a tunnel thruster installed in the bow or stern of a vessel with one or two propellers driven by an electric or hydraulic motor.
The relatively high costs of employing tugboats for every arrival and departure from port for commercial vessels was reasonably the main force behind the first thruster developments. Installing one or more thrusters on these large ships made sense also surpassing the point of running cost reductions, as they increased the vessels manoeuvrability and thereby increased safety in crowded waters.
In the mid-1980s, a few boat equipment manufacturers recognised the benefits that a bow thruster could provide for all boat types and sizes and the development and production of the first thrusters for leisure boats hit the market.
For many years tunnel-based bow thrusters were open to the market however, at that time the products were considered to be relatively expensive accessories. But as average boat size increased steadily from year to year and the ports did not many boat builders now saw that such a docking aid offered tremendous support for boaters in the increasingly crowded and tight harbours.
Today, there is a thruster for virtually any boat, regardless of hull type, material or size from about 20 feet and upwards. The standard tunnel-based thruster is still the leading choice for most boat builders, but as the market has matured, the requirements for installation flexibility and increased thrust has led to many redesigns, allowing for a well-functioning thruster solution for almost any vessel out there.
The most common thruster categories in the market today:
Running your vessel in the open sea is a breeze, but come to a busy overcrowded or tricky harbour, and you may feel your blood pressure rise. As a mariner, you might have experienced that in these conditions manoeuvring your vessel can be far more demanding than it seems.
Calculating Wind, ocean current, tides and other crafts' presence create a chaotic three-dimensional dilemma in the brain, wishing you had the mind of an Apollo space astronaut.
Well, with one or more thrusters on board, you gain one of the most important factors to reduce stress while docking, which is time. Time to orient yourself, time to consider and plan, and time to wait for others!
Main benefits of a bow and stern thrusters on board:
Many boaters tend to have a lifelong relationship with the sea. Unfortunately, as age slowly takes its toll, handling your vessel becomes more difficult. But this is where a proportionally controlled thruster system can keep your passion for the sea thriving and well. With proportionally controlled bow and stern thrusters onboard, you can pin the boat in the desired location and come alongside the dock and operate even a large vessel single handily the same way.
Few boat owners will voluntarily accept the cost or labour to replace a pre-installed thruster, even if it does not perform as desired. So, picking the right thruster the first time is crucial for many years of operation after installation. The right thruster is energy efficient, quiet and powerful enough to help you in the worst possible conditions when the thruster is needed the most.
The most critical factors for choosing the right bow or stern thruster are:
In our experience, there are two main common problems.
A bow or stern thruster that cannot deliver adequate thrust when you get caught in windy conditions while docking when you genuinely need the assistance of a thruster to control the vessel is undoubtedly a poor investment.
Here are three common reasons why a DC electric thruster may perform less than desired, whereas point 1 is quite common:
There is also a lot that can be done to reduce the noise produced by a thruster. The most important is to make sure the tunnel installation has been optimised. A thruster installation that screams throughout the harbour is usually due to incorrect installation.
To achieve a noise level acceptable to most people, one should:
Furthermore, it is important to keep in mind that the bow of a boat may act as a speaker membrane when vibrations are applied. If you are very unlucky, the propeller will generate a frequency that resonates with the hull's natural frequency, which in turn creates a powerful gain in noise. Traditional sound attenuation used in cars and the like can make a big difference.
However, check that the material is suitable for maritime use.
For many vessels, there are several possibilities to upgrade or improve an existing installation.
Typically, a side thruster will represent a low proportion of the boat's total cost, especially when buying a new boat. For retrofitting it is a bit more complicated, as it will vary considerably from boat to boat depending on how accessible the area for installation is and the running of cables.
Our best recommendation to obtain a decent understanding of the overall cost is to contact an experienced installer and ask for an actual offer based upon his or hers experience from similar boats or by letting the installer do an actual inspection of your vessel.
A stern thruster installation would typically be an easier installation without the need for fibreglass work unless the thruster model is a retractable version.
A thruster will generally require little maintenance and have low operating costs after installation. If you follow the manufacturer's maintenance plan, which mostly involves regular cleaning, replacement of sacrificial anode and general inspection, the thruster can work excellently for many, many years.
Sleipner Motor AS are dedicated to helping you understand your own needs and technical specifications to find the best thruster system for you, with more than 40 years of development and production experience of thruster systems.
Please see our distributor and dealer overview to find a local Side-Power representative who can guide you further in the process of securing a good solution for your boat.
If you cannot find an answer to a question in this article, you are welcome to send us an inquiry here.
We wish you lots of great times at sea, also in port!