Mercury - 1st Mate Safety & Security System Universal Dual/Triple Engine Kit 98-8M6007940. Overview. Large multi-engine boats carry more people, more power, and more responsibility. The Mercury 98-8M6007940 1st Mate Dual/Triple Engine Kit adds an extra layer of protection by giving the captain and passengers immediate overboard alerts and a built-in theft-deterrent system. Designed to work with all leading engine brands, this kit brings the core 1st Mate safety features to dual- and triple-engin