Cummins Marine Diesel Repower Specialists Seaboard Marine Stocks A Full-Line Of Cummins Marine Diesel Engines, ZF Marine Transmissions, And Specializes In Parts & Service For Cummins Marine. Seaboard Marine delivers “Guaranteed Better Than Factory” Performance, Parts, Design, and Engineering for Cummins and other Marine Diesel applications. We’ve been serving local Ventura County, California since 1980 as a custom boat builder, repower specialist, designer, and supplier of equipment to builders, commercial fishermen, and recreational users.