One of the most commonly over-looked, but important maintenance points on a RC boat is its stuffing tube/prop shaft area; so, keeping these parts properly serviced will help you avoid driveline problems when you run your boat. Done on a regular basis, the cleaning and lubrication of the hull’s stuffing tube, shaft and prop strut will allow them to function friction-free and the whole chore can be done with only a few hand tools. For our purposes, a fast electric drive will be cleaned and greased; however these same techniques will also apply to any nitro/gas hull as well.
The first step involved to service the hull drive will be to loosen the prop shaft from whatever type coupler is present on the motor/engine inside the hull. Either a locking-clamp or grub-screw coupler are used on your hull and our test FE boat required a 2mm Allen head driver to loosen the cable-retaining screw. A hardened-tip driver will provide the best fit on these coupler screws and once you can turn the propeller without any sign of movement from the motor, the boat’s transom strut must be separated to free the prop shaft.
With an inline aluminum strut/rudder setup the driveshaft removal chore was completed by unbolting the strut from its separate support bracket on the boat’s transom plate. To help ennsure that it is reinstalled and aligned correctly, I always mark the strut/bracket location with a felt-tip marker and then simply match the lines as I tighten the strut bolts. With the two strut screws removed the shaft assembly is slightly angled downward and then the unit came away from the hull stuffing tube.
KEEP IT CLEAN
To remove the old grease from the prop shaft, regular denatured alcohol and a paper towel works well and I recommend wearing rubber gloves to keep your hands and everything around you free of gunk. The stuffing tube can be swabbed-out with an alcohol-soaked flexible pipe cleaner sold at most craft stores. If your shaft passes through the strut, it too will need a good cleaning so that its bushings or bearings are free of any old grease/debris leftover from the lake. No heavy-duty solvents or auto brake cleaning spray should be used to clean the drive components as they can discolor your hull’s gel-coat or paint and could also damage the Teflon liner inside the stuffing tube itself.
Due to the high RPM and water contact that the boat’s driveline must live in, applying a marine-grade lithium grease to the stuffing tube, prop shaft and strut bushings will keep them spinning smoothly at all times. Aquacraft, Pro Boat and others market suitable RC boat shaft grease and I used the Pro Boat grease gun unit on the FE hull’s drive setup. The best greasing technique I’ve found for the flexible cable shafts is to run a good bead of the lube down the entire shaft and then use my fingers to work the thick grease into the cable’s wire strands and the solid stub shaft where the prop is mounted to the shaft. The strut features a greasing hole and the gun tip fits the opening perfectly. After passing the lubed prop shaft through the strut, I add a small dab of lithium grease to the end of the shaft and then insert the prop shaft into the hull via the stuffing tube. You should see some extra grease as the shaft exits the inner tube end as this will indicate that the entire tube/shaft lubrication has occurred and once you wipe off the excess grease from the shaft it can be secured back to the motor coupler.
• To clean dried grease out of a flexible drive shaft, a small wire brush will quickly dislodge the crud in your cable.
• A stuck coupler grub screw (due to thread compound) can be loosened by appyling heat from a high-watt soldering iron for a couple of seconds.
• Always leave a small gap between your greased shaft’s drive dog/strut junction to allow for flex cable movement.
Suffering a broken/snapped prop shaft while your boat’s at speed can also translate into a bent stuffing tube or a lost propeller and all of these problems can stem from a non-cleaned/greased hull drive. Taking the short time required to service the stuffing tube/prop shaft just makes good sense and your reward will be a trouble-free power craft when you toss it in the lake!
Words by Rick Eyrich