Bow thrusters are often seen as fit and forget items, but that attitude stands to eventually get you in trouble. Credit: Drozdp cc-by-sa-3.0
Today’s progressively larger boats are increasingly dependent on bow thrusters to manoeuvre in tight spaces. It’s common to think of these as fit and forget devices, with the owner and crew needing to know only where the trip switch that prevents the motor burning out in the event of a problem is located.
Granted, other problems are rare, but they’re by no means absent. Even with a new professional installation, debris becoming caught in the impeller may cause the shear pin to break. This is a weak link that prevents damage to the motor or impeller if it becomes suddenly jammed by debris. The unit’s manual will detail the shear pin replacement procedure. It’s usually a simple process, with the relevant parts being accessed from under the berth in the forward cabin – all you need is to have the spare parts accessible.
We increasingly rely on bow thrusters to manoeuvre safely in the confines of a marina, but what happens when the unit stops working?
Unfortunately many older systems receive no attention until a breakdown occurs. In most cases a little annual maintenance will all but eliminate any problems. It’s important to check the entire wiring circuit in as much detail as possible. Start by looking at any sections that are not hidden within conduit and examine them to check the condition of the insulation.
Bow thrusters are high-power devices that draw a considerable amount of current, which means that poor connections can easily result in a significant loss of energy. All connections should be dry and free dust and corrosion – if in doubt they can be dismantled, cleaned and reassembled.
In some cases installation problems come to light as a system becomes older. These are generally down to insufficient wire size – if a long length is needed, then the size may need to be substantial to avoid significant losses – or the lack of a decent battery with effective charging inputs close to the unit. As ever, it behoves any owner or skipper to both ensure the system is properly maintained, that they understand the function of all the elements and have the tools, spares and knowledge to undertake basic maintenance.