Refitting a boat trailer
Trailer refit: hubs and bearings, brakes, the lighting circuit, rollers and supports, and protecting the frame from corrosion.
A boat trailer works in exceptionally hard conditions: it is dipped in water, often salt, then dries out and travels roads salted in winter. That is a recipe for heavy corrosion, so refurbishing a trailer starts with a careful assessment of the frame. Clean off the dirt and loose rust, tap the critical spots, especially the box sections and welds, and look for perforation. A frame that has lost a serious part of its section is a hazard and needs welding or replacement, not paint.
The heart of trailer safety is the hubs and wheel bearings. Water, especially salt water, gets into the bearings when a hub that is hot from driving is launched and draws in moisture as it cools. Strip the hubs, wash the bearings, check the races and rollers for pitting and discolouration, and replace damaged ones as a set together with the oil seals. Pack the bearings with the right waterproof grease and set the end float to the instructions — consider fitting caps that keep the grease under pressure (bearing buddies).
Check the braking system if the trailer has one. Light trailers usually have an overrun brake with drums, which rust and seize after their dip in the water. Check the shoes, springs, cables and overrun mechanism, clean off the rust and grease the sliding points, and replace anything seized. The brakes must work evenly on both wheels, because uneven braking with a boat on board is dangerous.
Trailer wiring is a notorious source of faults, thanks to corroded contacts. It is best to replace the whole loom with a new one with sealed connectors and LED lamps, which stand up to shocks better than bulbs. Make the joints with crimp ferrules and adhesive-lined heat-shrink rather than twisted wires, and run the cables in a sleeve, away from sharp edges. Check that the position lights, brake lights, indicators and number-plate light work before every longer trip.
The parts that support the hull decide whether the boat survives transport undamaged. Check the rollers, shafts and carpeted bunks — cracked rubber and worn fabric scratch the gelcoat. Replace damaged rollers with new ones in durable plastic, re-cover the bunks with fresh carpet and set them so that the boat's weight is spread onto frames and stringers rather than single points. Check the winch, its strap or rope and the bow eye too, because these are what hold the boat while you drive.
Protecting the frame against corrosion extends the life of the whole trailer. Once cleaned back to bare metal, apply an anti-corrosion primer and an abrasion-resistant topcoat, and treat the inside of the box sections with a penetrating wax product. Replace fasteners with galvanised or stainless ones, and after every launch in salt water rinse the whole trailer with fresh water, including the brakes and the area around the hubs. That is the cheapest and most effective protection there is.
Finally, check that everything is legal and take it for a test run. Inspect the condition and pressure of the tyres (trailers often stand for years, and rubber ages regardless of mileage), the working of the coupling, the safety chains or breakaway cable, and the plate and lights. Do a short check drive and afterwards feel the hub temperature again — a hub that is too hot signals a bearing set too tight or a binding brake. Keep a record of bearing, brake and tyre inspections, and treat the trailer as seriously as the boat itself.
Material prices — products and options
Indicative prices in EUR (incl. VAT), as of July 2026. Products widely available in Europe; prices depend on the shop, the pack size and consumption. The links lead to example shops that ship across the EU. Dollar amounts are converted at 1 EUR = 1.1622 USD (ECB, 7 September 2026) and rounded — treat them as a rough guide, not a price in a US shop. Imperial values in brackets are conversions of the metric figure.
Hub bearings and seals
- Knott / AL-KO — hub bearing kit
waterproof bearing set with seals for boat trailers€15–45 (≈$17–52) - Single hub bearing (34×64×37 / 39×72×37)
replacement taper bearing for 750–1800 kg (1653.5 lb–3968.3 lb) axles€10–25 (≈$12–29) - Bearing Buddy — hub cap / grease fitting
cap that keeps grease pressure up and water out€10–25 (≈$12–29)
Axles and overrun brakes
- Knott / AL-KO — trailer axle 750–1800 kg (1653.5 lb–3968.3 lb)
complete axle with waterproof bearings (to replace a worn beam)€120–400 (≈$139–465) - Knott / AL-KO — overrun brake shoes and cables
set of shoes, Bowden cables and springs for a braked axle€20–90 (≈$23–105)
Rollers, shafts and bunks
- Keel / side / bow rollers
rubber or polyurethane rollers that will not mark the hull, various shapes€4–15 (≈$5–17) - Bunk carpet
carpet covering for the hull support bunks€10–40 (≈$12–46)
Wiring and lighting
- LED lighting set for the trailer
waterproof LED rear lights with a loom and a 7/13-pin plug€25–80 (≈$29–93) - Crimp ferrules with heat-shrink sleeving
watertight joints for repairing the wiring loom€8–20 (≈$9–23)
Corrosion protection
- Owatrol / Brunox — rust converter and primer
stabilises rust and primes a corroded frame€12–35 (≈$14–41) - Zinc / topcoat paint for the frame
anti-corrosion coating for a galvanised or painted frame€8–25 (≈$9–29) - Cavity wax for box sections
protects the inside of the frame sections from corrosion€10–25 (≈$12–29)