Nav Lights
According to USCGAUX,,see the link,,but if you want my opinion, on an 18' Boat, I would follow the below 7meter Rule. On my SanJuan24 I use to keep a set of Battery Nav Lights in a Locker, just in case my Main Lights went out. I still have em and will stow them with Fresh Batteries on my Hunter22. Whenever I first get a Boat, I first make it Safe for all concerned, then I start in on the finer points of Rigging and such.That BoatSafe site has lotsa info. But nothing beats a USCGAUX Safety Inspection, they are free from most every USCGAUX Flotillas. The only cost is if you dont do it and get pulled over and fined for not haveing the proper Gear. Happy Sailing