Marine environments place rigorous demands on every component of the ignition system. The combination of water spray, salt exposure, full throttle acceleration and harsh vibrations all take their toll. The MSD pro-billet distributor is the strongest and most accurate distributor you can put in your boat. The housing is CNC-machined from a billet of 6061-t6 aluminum creating a housing with no porosity. Each distributor uses MSD's race-proven magnetic pickup to trigger the ignition control. Mounted just above the pickup is a mechanical advance assembly that is easy to adjust so you can dial-in an ignition curve to match your boat's application (except PN 8366). For marine use, the distributor cap is bolted to the aluminum base. There are two flame arrestor holes with brass screens machined into the base of the distributor to prevent ignition of gas fumes that may build up in the engine compartment. A special weather tight connector is supplied. Underwriter'S laboratory approved.