Underwater thrusters are widely used in RC boats, unmanned surface vessels, underwater robots, and diving propulsion equipment. Due to the harsh operating environment, these systems place very high demands on motor and wiring reliability. In real-world use, some users encounter problems such as overheating motor wires, melted insulation, or even completely burned cables. These failures not only interrupt operation but can also cause secondary damage to motors and controllers. In most cases, burned motor wires in underwater thrusters are closely related to the following three major causes.
Reason 1: Excessive Current Causing Cable Overload
The most common root cause of motor wire failure is excessive current over an extended period or during sudden load spikes. When the underwater thruster experiences abnormal load conditions—such as propellers entangled with aquatic plants, sand, or debris—the rotational resistance increases sharply, leading to a rapid rise in current. If the motor wires are undersized or made from materials with insufficient conductivity, they cannot safely handle the actual operating current. Continuous overheating then causes insulation aging, melting, or even conductor breakage.
In addition, mismatched battery voltage and motor specifications can also result in overcurrent conditions. Using high-voltage or high-discharge batteries to power a thruster designed for lower power levels forces the motor to operate beyond its rated capacity. In such cases, motor wires often become the first components to fail due to prolonged overload.
Reason 2: Waterproof Failure Leading to Short Circuits and Corrosion
Motor wires in underwater thrusters are constantly exposed to moist or fully submerged environments, making effective waterproofing essential. If cable joints are poorly sealed, heat-shrink tubing degrades, or the outer insulation becomes damaged, water can seep along the wire strands into the interior. This intrusion may cause localized short circuits or abnormal increases in electrical resistance. Short circuits generate extremely high currents in a short time, which can instantly burn motor wires, while long-term water exposure leads to copper oxidation and corrosion, degrading conductivity and generating excess heat.
It is also important to note that some motor wires may appear intact on the outside while internal corrosion has already occurred. This type of hidden water ingress is especially dangerous, as wire failure often occurs suddenly under high-load operation, increasing the risk of severe damage.
Reason 3: Poor Heat Dissipation and Improper Cable Routing
Although underwater environments generally offer lower ambient temperatures, this does not mean motor wires are immune to overheating. When wires are routed inside sealed compartments or tightly bundled with controllers and battery cables, heat dissipation can actually become worse. During extended high-power operation, accumulated heat may not be released effectively, causing localized temperatures to exceed the insulation’s thermal limits.
Improper cable routing further exacerbates the issue. Frequent bending, excessive compression by enclosures, or overly concentrated fixing points increase both contact resistance and mechanical stress. These stressed sections are more prone to heating and often become the weakest points where wire burnout first occurs.
Conclusion: Addressing Root Causes to Reduce Burnout Risk
Burned motor wires in underwater thrusters are rarely caused by a single factor; they usually result from a combination of electrical overload, environmental exposure, and structural issues. Properly matching motor and battery specifications, selecting cables with appropriate wire gauge and waterproof ratings, and regularly inspecting sealing and routing conditions are essential preventive measures. By addressing these factors at both the design and usage stages, users can significantly reduce the risk of wire failure, extend the service life of underwater thrusters, and ensure safer, more stable operation.