Ballast resistors? Circuit boards? Voltage regulators?
NOT GOING TO HAPPEN IN CHEAP LED ASSEMBLIES!
Guys, the typical "12 LEDs in this replacement bulb" has twelve LEDs and one (or a few more) voltage dropping resistors in it.
They're not called ballast resistors. There are no voltage regulators--and that's often part of the problem. Ancor or other brand, they're usually cheapo crap from China, because cheap LEDs can cost a nickel while good ones can cost ten bucks. EACH.
And using a resistor to brute-force limit the current to an LED or LED cluster can cost a penny, while a real voltage regulator will cost a quarter or even a buck if it is done properly with other compoments and, yes, a mini circuit boards.
LEDs in clusters like that are common on the back of trucks and busses BECAUSE THEY ARE CHEAP DESPITE BEING UNRELIABLE. A good marker lamp cluster could cost $200-300, a cheapo one costs $20 or less. Look at any city bus or truck on the highway, there are a dozen LEDs in each cluster and the odds are, two to six are burned out.
That's OK when your vehicle gets depot maintenance every six months and your purpose is to stay legally lit in between depot visits. If half the LEDs burn out and the cluster is thrown away every six months or year--that's still cheaper than the ticket for one burned out bulb.
The $200 cluster would last 50,000 hours plus, but anyone with a screwdriver could steal it in thirty seconds, so the cheap crap has a reason to be used.
Have you seen the LED tail/brake light clusters on a Mercedes or Caddy? The cost for all those LEDs is close to $1000 per vehicle, and that's when you buy enough LEDs to build 50,000 cars with them, too. OK, maybe by now it has dropped to $700. There's a reason you don't see mid-priced cars with LED tail lights! There's no cheaper way to do it reliably.
In your head compartment? Odds are that the LED cluster is burning out because of voltage spikes, surges, or a regulator problem on the boat. Check the voltage, if it is over 14.4 volts your regulator is the problem. If the voltage is good, then the odds are you are throwing spikes every time you start and stop the engine, and the spikes are burning out the LEDs.
That's not my opinion. The folks at CreeX, LumiLED, and other premium LED suppliers ($10 each) all specify SPIKE PROTECTION for ay type of vehicular use--or they void the warranty. Guess what? No spike protection in those cheap cluster bulbs, because it costs money. You can add it, for a buck or two (plus minimum order fees) per "bulb" socket. Or hold out for better clusters that have current regulation and spike protection built into them. If you ask the maker about this and they say "HUH?" that just means Chinese crap, which doesn't have them.
No mystery here, you get what you pay for--if you're lucky.