Every year, more and more boats are built with bow & stern thrusters, and boat-owners without them are installing them to make their boats more maneuverable. While they’re extremely helpful for docking and navigating in close quarters, they are often “out of sight, out of mind”. Because their thrusters are often buried deep in the bilge, many boaters don’t even know how to access them for maintenance.
As a result, very few boaters perform any annual maintenance on their thrusters, aside from changing anodes. Like any piece of equipment on your boat, thrusters require maintenance to operate at peak performance, and you don’t want your thrusters failing at the worst possible time. That’s why we’ve put together five helpful tips for maintaining your thrusters to keep them running strong. Keep in mind, not all thrusters are the same, so it always best to consult the owner’s manual for tips specific to your brand and model of thruster.
1. Replace the Anodes
While most everyone knows to replace anodes, this tip is still at the top of our list because it is the most important. A thruster gear-leg underwater with no anodes to protect it from corrosion will erode in a matter of days and cause major problems.
Anodes should be replaced yearly or when they are half-eroded. Prior to launch wire brush clean lightly eroded anodes to remove any oxidation after being exposed to air. When installing anodes, use blue Loctite on the anode screw.
2. Cleaning & Anti-Fouling
Any time the boat is out of the water, you should remove the props and scrape all marine growth off the gear-leg and propellers. Be very thorough in removing growth, as even barnacle feet left on the props will reduce performance and run time.
Be sure to grease the propeller-shaft with marine-grade grease before re-installing the propellers. The tunnel, gear-leg and propellers should also be painted with anti-fouling paint as the hull requires.
3. Check Operating Voltage
It is always important to make sure the batteries for your thruster are providing enough power. To ensure they are, it’s best to check the operating voltage. It is important to note that this check should only be conducted with the boat in the water, as running the thruster out of the water with no resistance will damage the motor.
The operating voltage is the voltage reading while the thruster is running for about 10 seconds. To check it, you will simply connect a volt-meter to the positive and negative terminals on the thruster motor and read the voltage while the thruster runs for 10 seconds. It’s usually easiest to check this with two people: one to operate the thruster from the helm, and the other to hold the volt-meter.
12-Volt thrusters typically run between 9.5V and 10.5V, while 24V thrusters typically run between 18V and 21V. If voltage is below 9V for 12V thrusters or below 17V for 24V thrusters, you have a low-voltage situation on the boat. Operating the thruster at low voltage will damage components on the motor like the solenoid, so if that is the case on your boat, a qualified marine technician should look into the cause of low operating voltage.
4. Check Gear-leg Oil (if applicable)
Some older-models of thrusters require an oil bottle and tube to feed oil into the gear-leg. If you do not have an oil-fed gear-leg, you likely have one that is pre-filled and sealed at the factory, and you can skip this step.
Check the gear-leg oil feed tube for water. If the oil is milky, there is likely a water leak and the gear-leg should be serviced by a qualified marine technician.
Check the gear-leg oil reservoir level. If more oil is needed, consult the owner’s manual and add the proper type of gear oil recommended by the manufacturer. In most cases, an 80-90 or 85-90 weight gear oil will work.
The gear-leg oil should be changed every two years under normal recreational use conditions. Remove the drain plug and allow fresh oil from the reservoir to flush out the used oil. Reinstall a new drain plug and gasket and top-off the reservoir as necessary.
Permanently sealed gear-legs do not require servicing.
5. Inspect Thruster Compartment
Beyond inspecting the thruster itself, be sure to inspect the compartment in which the thruster motor is mounted as well. The thruster motor creates heat with prolonged usage. It is important that there are no objects in contact with the motor.
Is the compartment dry? If not, make sure to dry it and find the source of the water. The less moisture the better, so do not store any wet or damp items near the thruster motor.
Thruster motors can also create carbon dust, so if there is a thin black film or dust in the compartment, that’s perfectly normal, but you may want to wipe it up. You may also want to remove the motor cap and use a vacuum or compressed air to remove the excess dust that’s collected in the motor itself. Please note carbon dust is harmful to breathe, so always wear a mask when vacuuming or blowing out the motor.
Lastly, check all the electrical connections and make sure they are tight and free of corrosion.
Following these tips annually will help ensure your thruster runs at peak performance all season long. Be sure to consult your owner’s manual for any maintenance specific to the make and model of the thruster on your boat.