The phrase identifies a specific outboard motor model produced by Mercury Marine. It refers to an engine designed for powering boats, characterized by its 135 horsepower rating and distinctive “Black Max” branding, which signified a performance-oriented product line. Such engines were commonly used on recreational boats like fishing boats and runabouts.
These motors gained popularity due to their relative power, reliability, and availability during their production period. The horsepower offered a good balance for many common boat sizes, providing adequate thrust for watersports and general boating activities. Their robust design and the availability of parts contributed to their longevity and continued use by boaters.