Comprehensive Boat Trailer Maintenance and Corrosion Prevention Guide

Before mechanical work, the trailer must be chemically decontaminated. Mix your salt neutraliser at a 1:500 ratio in a foam cannon or pump sprayer. Coat the entire frame, focusing on the inside of the C-channel or box sections. Allow it to dwell for 10 minutes (do not let it dry) before rinsing thoroughly with fresh water. This prevents you from grinding salt crystals into moving parts during the service.

While the trailer is wet, look for 'bleeding' rust—orange streaks coming from bolt holes or welds. Use a high-intensity LED torch to inspect the inner faces of the wheels and the underside of the axle. In Australia's heat, check tyres for 'dry rot' or sidewall cracking, which indicates UV damage. Ensure the trailer is on a level, hard surface (concrete) before proceeding.

Chock the wheels on the opposite side of the trailer to prevent movement. Loosen the wheel nuts slightly (half a turn) while the tyre is still on the ground. Position the hydraulic jack under the main frame rail or the axle seat (never the centre of the axle tube). Lift until the tyre clears the ground by 50mm and secure with a jack stand.

Lay out a clean lint-free rag or magnetic tray for small components like split pins, washers, and bearings. Contamination is the primary cause of bearing failure; a single grain of outback red dust can act as an abrasive that destroys a bearing race within 100km of travel.

Remove the dust cap or bearing protector using a rubber mallet. Straighten and remove the split pin, then unscrew the castle nut. Carefully pull the hub assembly toward you, catching the outer bearing as it slides off the spindle. Use brake cleaner and a clean rag to strip all old, discoloured grease from the spindle and the internal hub cavity. The metal should be 'surgical' clean before inspection.

Inspect the rollers and the bearing race (the ring pressed into the hub) for 'pitting', 'bluing' (heat damage), or scoring. If you see any dullness or physical indentations, the bearings must be replaced as a set. In Australia’s summer, heat-stressed bearings often show a straw-coloured tint; this is a sign of lubricant failure and requires immediate replacement.

Place a glob of marine grease in your palm. Press the edge of the bearing into the grease repeatedly until it forces its way through the rollers and exits the top. Rotate the bearing and repeat until the entire circumference is saturated. This 'packing' ensures no air pockets remain, which is critical for preventing water ingress during submersion.

The rear grease seal is the most common failure point. Pry out the old seal and discard it. Apply a thin layer of grease to the outer edge of a new double-lip marine seal and tap it into the back of the hub using a flat block of wood to ensure it sets level. A crooked seal will leak grease and allow saltwater in immediately.

Slide the hub back onto the spindle, followed by the outer bearing, washer, and castle nut. Tighten the castle nut to 25Nm while spinning the hub to seat the bearings. Then, back the nut off about a quarter turn until it is finger-tight and the hole for the split pin aligns. There should be a tiny amount of 'play' (0.1mm) to allow for thermal expansion during highway towing.

Tap the bearing protector into the hub. Use a grease gun to fill the protector until the internal spring compresses and the piston moves outward. Stop immediately when the piston reaches the 'full' mark. Over-filling can blow out the rear seal, causing grease to coat your brake pads or magnets, rendering them useless.

Leaf springs are prone to 'pack rust' between the leaves. Use a wire brush to remove loose scale. Apply a liberal coating of Lanolin spray to the entire spring pack, hangers, and shackles. Lanolin is non-toxic to marine life and creates a hydrophobic barrier that salt cannot penetrate. This also reduces the 'squeak' common in dry Australian conditions.

For mechanical overrun brakes, check the cable tension. There should be enough slack so the brakes don't drag, but they should engage when the coupling is compressed. Lubricate the sliding master cylinder at the front of the trailer using a general-purpose grease. If you have hydraulic discs, check the pad thickness (minimum 2mm) and look for weeping fluid at the calipers.

Open the 7-pin or 12-pin trailer plug and spray the terminals with a contact cleaner. Once dry, pack the back of the plug with dielectric grease to prevent 'green crust' (copper oxidation). Check all LED lights for cracked housings; even 'submersible' lights can fail if the UV-weakened plastic cracks and allows salt spray inside.

Set tyre pressures to the manufacturer's specification (usually 45-60 PSI for light truck trailer tyres). Reinstall the wheel and tighten nuts in a star pattern. Lower the trailer and use a torque wrench to tighten nuts to 125Nm (check your specific manual for variations). Check the spare tyre pressure; it is often neglected and found flat when needed in the middle of the Nullarbor.