Blue Opal, as fitted from the factory, has eleven 10W halogen bulbs. Not only do they draw 1.1 amps each (according to my bench power supply, and basic electronics knowledge), they get really hot and heat up the light fixture too. Having confirmed that they’re all G4 bulbs, a quick rummage on Amazon found a ten-pack of LEDs that seem like they’ll do the trick. I tested them on the bench power supply to confirm that they worked, and yep, 0.11 amps per bulb. So the house lighting won’t kill my batteries as fast as they could before – this is particularly important given there’s a switch in the companionway that bypasses the house battery keys, and it’s wired to a 10W bulb. It’s easy to bump against it and turn the light on as you’re locking up, so I’ll be replacing the switch anyway, but it’s nice to know that the drain is now 1/10th of what it was before.
Alas, the process of replacing the fixtures has resulted in half of them breaking (and one of them was broken even before I tried to remove it), so now I’m on the hunt for replacement units.
For anyone else with these fittings, here are some words of caution – the metal tabs that the springs sit on are not strong; the process of pulling the fitting downwards out of the hole results in a lot of stress being applied to the tabs that the springs sit on, and the old metal just breaks. They’re 65mm internal diameter, 25mm high, and the flange is about 80mm diameter. Found some replacements in America, but have to check whether they actually have them (Imtra Newports) in stock, and then arrange shipping. Or go back to hunting on eBay.