Not very well. It's 20 watts about 20 or so feet above. It will help you see where you're walking to avoid tripping and such, but if you need to do real work consider adding additional lighting. Its not hard to do. You can mount it to either the spreaders or the side of the mast. Use the same wiring. If the wiring is too small to support extra current, then add LED lights. Most likely the wires can support that.How well does it light the foredeck at night?