Every gearcase seal in fact has two individual seals. The internal seal works to keep the oil In the gear case, plus the outer seal retains the water out. The benefits of early issue detection, cost financial savings, and enhanced reliability all underscore the importance of making the lower unit https://outboard-lower-unit-gear39695.wikibuysell.com/1470038/5_simple_statements_about_mercury_outboard_motor_sizes_explained