Another outboard starter we are selling is part no. 3421. It has 10 tooth drive gear.  This will fit your Yamaha outboard motor. When buying this starter, the year of your Yamaha outboard must be 1984 to 1997 with the horsepower of 9.9 to 15 and 1988-1998 for 25 horsepower. You can also use this to replace your Hitachi engine starter S106-07B, S106-07E and S106-07F.