Bulb
I have a 28.5 and it has a Perko light model 1331DP which takes a Perko FIG-71 bulb which costs about $4.50 for a two pack. You will probably also want to replace the lens which no doubt is clouded up by now and that is another $8.00 dependent on who you get it from. Boat US has the best prices on these two items.Now the fun part with the Perko is that you will need to unscrew two long bolts to remove the light from the mast. Then you will need to remove the bracket from the light. Then you will need to unscrew two small screws that alows you to remove the chrome metal top so you can get to the bulb. Don't lose the screws or top. This will be a lot of fun swinging from a bosun's chair. I am going through the same problem right now and have opted to get a new light. I've ordered an Aqua Signal 25, 20 pt, for $11.30 ( used JSI on line catalog for a best price) and the bracket for $7.95, using Defender for a best price. I think it is a superior light and now all of my navigation lights use the same bulb.I don't know if you have the Perko but they are pictured in the West catalog so you should be able to eyeball it.Good luck.