The Balmar 6-Series alternators combine the best of traditional Balmar quality with technology that is both more universal and more user-friendly than ever. The 6-series is the first high-output alternator that gives you the choice of either using its internal regulator or connecting to an external smart regulator. Patented Smart Ready internal regulation offers the 6-Series alternator the unique ability to be used as a stand-alone high-output OEM replacement for performance ski and wakeboard tow boats, day cruisers, or workboats, which have more electrical loads than ever! For sailors or power boaters demanding the very best in multi-stage external regulation, the Smart Ready system provides a dependable back-up for external voltage regulators. Isolated Ground terminals are now standard, improving the system ground and noise reduction. 6-Series alternators utilize dual internal fans and an open frame case design for improved alternator cooling. A universal crown assures an easy fit on most modern engines. Model 604 alternators replace 4"ID saddle mount alternator models. Low amperage (D+) lamp circuit is included. Dual internal fans provide added cooling. Alternator comes with Patented Smart Ready Internal Regulation, corrosion-resistant powder-coated cast aluminum case and five-way universal tensioning crown. Ignition-safe for marine gas or diesel engines.