Can I run LED spreads off the cranking battery?

You can, briefly. A dual-battery setup with the lighting on the house side is the grown-up trailer-boat answer. If you only have one battery, keep lighting modest and fused, and do not idle a light bar while you fish for three hours.

Are automotive LED bars OK on a boat?

Some survive. Many do not, because they are not built for washdown, and because the beam may be illegal as a navigation or steaming light. Buy marine IP67 fittings for anything that lives in weather.

Do courtesy lights need to be dimmable?

On a trailer boat, a warm courtesy pair that you can switch off is enough. Dimming matters more once you have a helm full of glass and a night exit through a bar.

Marine lighting · 10 min read · Updated 2026-08-28

Marine LED lighting for Australian trailer boats

A 12-volt trailer boat can look like a flybridge and then fail to start. This is how to light a tinny or a 7-metre fibreglass hull without flattening the cranking battery.

A small pleasure boat on the Southport Broadwater

Trailer boats are where Australian marine lighting goes to get over-specified. The Facebook photo wants a Lumitec-style transom wash, a light bar on the rocket launcher, courtesy pucks in the carpet and a spot for the ramp. The electrical system is still a single cranking battery and a 4 mm cable.

The old AM Wholesale lighting range included compact courtesy and flood fittings for exactly this hull. The constraint is not the SKU. It is the battery.

The legal lights come first

Before atmosphere, fit COLREGs-compliant navigation lights that still work when the stereo is off. A trailer boat that leaves before dawn on the Broadwater is a vessel, not a car park. White all-round, or the proper sidelight and stern combination for your length, beats a pretty RGB strip.

Then the work lights

A spreader or a compact flood that points at the deck, the transom and the ramp is the useful second circuit. Read spreader and flood lights for night fishing before you buy a 50,000-lumen claim. On a 6-metre hull, a sealed marine flood in the 1,000-lumen class, aimed down, will do more than a light bar aimed at the next skipper.

Then atmosphere

Courtesy pucks, gunwale strips and underwater pairs are last. They should live on their own fused circuit, preferably on a house battery isolated from cranking. See dual-battery systems for trailer boats.

Cable, fuse, switch

Marine-rated cable, not figure-eight from the automotive aisle.
A fuse at the source, sized to the cable, not to the LED’s manners.
A switch you can find with wet fingers.
Strain relief where the cable leaves the hull or the transom.

IP67 on the lamp does not make the join immortal. Queensland UV will finish any fitting whose gland was a hope.

A sane trailer-boat package

Navigation lights, one deck flood, a pair of courtesy LEDs, and — if the battery and the hull allow — a compact underwater pair. That is a lighting job. A nightclub is a second battery and a second invoice. For cruisers with house banks, step up to the marine lighting hub and onboard power.

Frequently asked questions

Can I run LED spreads off the cranking battery?: You can, briefly. A dual-battery setup with the lighting on the house side is the grown-up trailer-boat answer. If you only have one battery, keep lighting modest and fused, and do not idle a light bar while you fish for three hours.
Are automotive LED bars OK on a boat?: Some survive. Many do not, because they are not built for washdown, and because the beam may be illegal as a navigation or steaming light. Buy marine IP67 fittings for anything that lives in weather.
Do courtesy lights need to be dimmable?: On a trailer boat, a warm courtesy pair that you can switch off is enough. Dimming matters more once you have a helm full of glass and a night exit through a bar.