Mercury, 6-15HP - 2 1/2 Gearcase - 8 tooth spline, 6HP (2-Stroke) 1986-, 8HP (2-Stroke) 1986-, 9.9HP (2-Stroke) 1986-, 10HP Seapro/Marathon 1995-2010, 15HP (2-Stroke) 1986-, 15HP (4-Stroke) 1989-2006, 15HP Seapro/Marathon 1995-2010, Force 9.9/15HP 1996-98