Ed,
Are you looking for the tri-color replacement bulb or the anchor light bulb? Is this a Series 25 or Series 40? There are pors and cons to replacement bulbs.
Pro's =
-Bulbs can be replaced if they fail (which they do)
-Can be less expensive to upgrade
Con's =
-Most all (with the exception of a couple Dr. LED bulbs in certain Aquasignal fixtures) are not USCG certified and you may not technically meet the requirements of a "nav light" with them.
-If mounting behind a colored lens you ideally need red behind red, green behind green and white behind clear.
-Many aftermarket bulbs sold by "best value" resellers have no voltage regulation or circuitry to keep noise out of your VHF.
-Many aftermarket bulbs fail in old fixtures because they are not designed to handle the condensation that can occur inside them. Purpose built lights by the likes of Hella, Aquasignal & some others can last significantly longer.
-Many aftermarket bulbs can not handle the heat inside an existing nav light fixture and a not properly heat sinked to do so. Purpose built lights have massive aluminum heat sinks.
LED lights are GREAT from a low draw perspective but have some drawbacks. If buying LED's I prefer buying from either Hella or Aquasignal. Neither of these companies rushed their LED specific nav lights to market and both did extensive testing of them in the marine environment. Out yacht club launches were converted to Lopo Lights four years ago. Both launches are now back to using incandescent bulbs after multiple failures of the Lopo's. The Lopo's are VERY, VERY expensive so price does not always drive longevity.. I suspect that the solenoid on the starter motor on these launches has contributed to the failures but Lopo claims they are spike protected. When solenoids close, and that field colapses, they can throw some serious spikes which some LED's don't like. Some starters are protected & some are not & some LED's are protected and some are not..
I have had two Dr. LED failures in my Aquasignal Series 40 anchor lights. I am on my third bulb. The next time it will definitely be a dedicated purpose built LED anchor light from Aquasignal. I also own a Marine Beam bulb that corroded so badly inside the Series 40 due to condensation that I had to yank it. Purpose built nav lights are designed to deal with these issues better.
In contrast our series Aquasignal Series 32 LED nav lights have not given us one hint of an issue in over three years, except for the lightning strike, which killed everything...
