What's the model number of your engine, and which website are you using to look at the Yamaha parts?
EDIT: OK, just found a site to view Yamaha parts on, and yes, they like very similar, and given that the early small Mariners were actually re-badged Yamahas I'll say the likelihood of it being the same part is very high.... But I do need your engine model number (not serial number, model number) to verify the year/series of your engine...
Chris......