Boat Trailer Wiring for Perth Boat Ramps

This guide is for Perth boaties who launch from the river, the coast or the Peel waterways and are tired of trailer lights that work one weekend and fail the next. It explains how salt water attacks trailer wiring, what to fit, and a simple routine that keeps the lights working after every launch.

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Where Perth boaties launch

Perth has a lot of public boat ramps, and the WA Department of Transport keeps a list of the metropolitan boat ramps. On the Swan and Canning rivers, they include Coode Street in South Perth, Point Walter, Deepwater Point at Mount Pleasant, Clarkson Road at Maylands and Hackett Drive. On the coast, Hillarys Boat Harbour is a popular launching spot in the northern suburbs, with Ocean Reef further north.

South of the city, Rockingham has ramps at Palm Beach and Point Peron, and Safety Bay has more. In Mandurah, the list includes Mary Street, Dolphin Pool and the Dawesville Channel. Wherever you launch, most trailers end up backed into salt or brackish water. The lower Swan River is an estuary, so it is not a fresh water escape from salt.

What salt water does to trailer wiring

Salt water conducts electricity and attacks copper, steel and the brass and tin used in connectors. Once it gets into a joint, a plug or a lamp, it keeps working long after the boat is back in the shed. The result is green or white corrosion that slowly blocks the current. Lights get dim, flicker, or stop working one at a time.

Incandescent lights have an extra weakness. The globe is hot when you back the trailer into the water. Cold water on hot glass can crack the globe, and as the air in the lamp cools it contracts and draws water in through any gap in the seal. That water stays there and corrodes the globe holder.

The earth is often the real culprit. Many trailers earth their lights through the frame and rely on the towball and coupling for part of the circuit. Salt, rust and paint stop that path working well. When the earth is poor, the current tries to find another way back, which is why you sometimes see one light glowing faintly when a different light should be on.

Fit submersible LED lights

The single best upgrade for a boat trailer is a set of sealed, submersible LED lights. They have no globe to crack, run cool and draw very little current, so a slightly corroded connection is less likely to stop them working. Look for lights sold as submersible or rated for marine use, and for sealed leads rather than open terminals.

Keep the wiring as simple as possible. Run a dedicated earth wire from the plug to every light rather than relying on the trailer frame. Mount the lights as high as the rules and the trailer design allow, and some boaties fit their lights on a removable light board that comes off before launching. Check that any change you make still meets the lighting rules for trailers in WA.

Better joins and a better plug

Every join in a trailer loom is a place for salt water to get in. Use as few joins as you can. Where you need one, use quality crimp connectors with adhesive-lined heat shrink, so the join is sealed when it is heated. Avoid twisted and taped joins, and avoid household connectors. Our guide on crimping wire connectors shows the method.

Use cable rated for automotive or marine use. Tinned copper wire resists corrosion better than plain copper and is worth paying for on a boat trailer. Run the loom inside the frame or in conduit where it is protected from the ramp, and clamp it so it can't flap or rub. For the plug itself, a quality 7-pin flat plug suits most boat trailers. See how to wire a 7-pin trailer plug if you are replacing one.

A routine for every launch

A few habits at the ramp make a big difference to how long your trailer wiring lasts:

• Unplug the trailer from the car before you back into the water, and let incandescent lights cool first.
• Keep the car's plug off the ground and away from the water while you launch.
• Hose the trailer with fresh water as soon as you get home, including the lights, plug and loom.
• Let the plug and lights dry before you connect them again.
• Smear a little dielectric grease on the plug pins and in the socket every few months.
• Check all lights before you leave the ramp, not halfway home.

A note on boat trailer brakes

Larger boats need a braked trailer, and the WA rules on trailer brakes are based on the trailer's loaded mass. Brakes go in the water too, so many boat trailers use override brakes or systems built for immersion rather than standard electric drum brakes. If your trailer has any electrical brake components, they need the same rinse-and-check care as the lights. Have the brakes inspected if they feel weak or uneven, and check the WA towing rules for your trailer's mass.

Finding a fault after a launch

When lights fail, start at the plug. Clean the pins on both the car and the trailer and check for corrosion. Then test each circuit with a multimeter at the trailer plug and at the light. If the voltage is there but the light won't work, the earth is the next suspect. Our guide on why trailer lights stop working has a full step-by-step.

If the loom is badly corroded, rewiring the whole trailer is usually quicker and more reliable than chasing faults joint by joint. Auto electricians near the coast do a lot of this work. See our Kwinana and Rockingham and Mandurah pages, or Fremantle if you launch on the river.

Parts for this job

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Get it done: get a quoteDo it yourself: shop submersible trailer lights

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Questions Perth drivers ask

Why do my boat trailer lights keep failing?

Salt water gets into the plug, joins and light housings and corrodes them. Incandescent globes can also crack when hot glass hits cold water, and lamps draw in water as they cool. A poor earth through a rusty frame or coupling adds to the problem. Sealed LED lights, a dedicated earth wire and a fresh water rinse after every launch fix most cases.

Should I unplug my trailer before launching?

Yes. Unplugging stops current flowing through wet connections, which slows corrosion, and lets incandescent globes cool before they hit the water. It also keeps the car's socket out of harm's way. Plug back in once the trailer is out of the water and the plug has drained, and check every light before you drive off.

Is the Swan River less damaging than launching at the coast?

Not by much in the lower reaches. The lower Swan River is an estuary and the water near Perth can be salty or brackish, so it can still corrode trailer wiring. Treat a river launch the same way as a coastal one: unplug before launching and rinse the lights, loom and plug with fresh water afterwards.

Are LED trailer lights worth it on a boat trailer?

For most boat trailers, yes. Sealed submersible LEDs have no globe to crack, run cool, last longer and draw less current, so small amounts of corrosion are less likely to stop them working. Buy lights rated as submersible or for marine use, and pair them with good sealed connectors and a dedicated earth wire for the best result.

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