MSD recognized the need for a true marine performance distributor and built this Pro-Billet MSD 8560 marine distributor to answer this need. Marine environments place rigorous demands on every component of the ignition system, especially the distributor. The combination of water spray, salt exposure, full throttle acceleration, and harsh vibrations all take their toll. The housing is CNC-machined from billet 6061-T6 aluminum, creating a housing with no porosity or weak areas. Internally, a Tuftride coated steel shaft is guided by a sealed ball bearing and an extra-long sintered bushing for high-speed stability and endurance. Each Chevy marine distributor uses MSD's race-proven magnetic pickup to trigger the ignition control. The pickup receives its signal through a precision-manufactured reluctor that is attached to the shaft. The mechanical advance assembly receives a QPQ plating for long lasting resistance to corrosion in marine environments. Their mechanical advance assembly is easily adjustable, so you can dial-in an ignition curve to match your boat's application. Three additional sets of advance springs and stop bushings are included with detailed instructions, making adjustments easy to perform and understand. The distributor cap is bolted and sealed to the aluminum base, and has two flame arrestor holes with brass screens machined into the base of the MSD 8560 marine distributor. This design works to prevent ignition of gas fumes that may build up in the engine compartment. A special weathertight connector is supplied to provide a positive lock and water-resistant connection. This heavy-duty connector will withstand high temperatures and water, and plugs directly into the MSD 6M-2 or 7M-2 ignitions. The Chevy marine distributor comes complete with a high-quality, bolt-down alkyd cap and MSD's racing rotor. These high-quality distributors have been tested by the Underwriter's Laboratory, and are certified to meet or exceed safety standards for marine ignition systems as set by the U.S. Coast Guard. They require the use of a separate ignition box.