What should I look for in a boat trailer for use in salt water?
I'm buying a trailer for my 5.5-metre motorboat and will be launching into salt water most weekends. What should I look for in the frame, brakes and bearings, and which features are worth paying extra for?
Answer
Choose a hot-dip galvanised steel or properly built marine aluminium trailer with enough payload for your fully equipped boat, accessible running gear and brakes designed for regular immersion. Check the loaded weight first: overloading damages tyres, bearings and suspension regardless of the trailer's resistance to salt.
Check weight and hull support
Brochure displacement commonly describes an empty standard boat. Fuel, batteries, the outboard, anchors and cruising equipment can add considerably to that figure. Use a weighbridge where possible, and check whether the quoted boat weight includes its engine.
Trailer payload is its permitted laden weight minus its own unladen weight. A trailer plated for 1,800kg that weighs 400kg can carry only 1,400kg. If your equipped boat weighs 1,300kg, a 2,000kg trailer of similar construction gives more capacity for additional gear.
- Check the towing vehicle's permitted towing weight, gross train weight and towball load, plus the coupling and trailer limits.
- Choose adjustable bunks or rollers that support the hull where its builder specifies, with proper support beneath the transom and engine.
- For a sailing boat, confirm how the keel load is carried; ordinary motorboat rollers may be unsuitable.
- Check local width, braking and driving-licence requirements before buying, particularly for travel abroad.
The axle position must allow the correct noseweight without leaving the stern unsupported. Ask the supplier to set up the trailer for your hull.
Inspect frame and salt traps
Hot-dip galvanised steel is a sound choice that can be repaired widely. Look for galvanising applied after fabrication, including around welds, and drainage openings that let hollow sections empty. Painted mild steel alone needs much more attention after repeated saltwater immersion.
Marine aluminium saves weight and avoids red rust, but check its welds, axle attachments and contact points with steel or stainless fittings. Dissimilar metals need suitable isolation. Stainless bolts alone do not make the assembly corrosion-proof.
On a used trailer, examine the underside of crossmembers, spring hangers, U-bolts, drawbar and winch-post base. White deposits can occur on galvanising, but investigate heavy scaling, swollen joints, deep pitting or cracks. Fresh paint over these areas can conceal deterioration.
Choose replaceable fasteners and brackets that are readily available. Check that rollers turn freely, bunk coverings are secure and adjustment bolts remain accessible with the boat aboard.
Check bearings, brakes and spares
No hub is permanently immune to seawater. Ask which bearings, seals and brake parts the trailer uses, how they are serviced and whether a local trailer specialist stocks them. AL-KO and Knott running gear is common on European trailers, but identify the exact axle and brake model.