🚤 Flex Shaft
A flexible driveshaft running from motor to propeller, letting the motor be mounted rigidly while still tolerating slight hull flex and vibration.
What it actually does
The flex shaft is the flexible steel cable that carries drive from the motor to the propeller in most RC boats. It has to transmit full power while curving through the hull, which is why it needs regular attention.
In practice
It runs inside a stuffing tube and must be greased before every outing — the grease both lubricates and helps keep water out. It is normally supported at the propeller end by a strut. Over time the cable can unwind or develop a set, at which point it should be replaced.
Worth knowing
A dry flex shaft is the most common cause of an overheating boat drivetrain. Greasing it takes a minute and prevents most flex shaft failures.