That's 11&1/8" diameter and 13" pitch. Don't know about the splines, but it's a bigger diameter than the Merc prop you'd have on a 1985 50hp as standard. Standard on yours is somewhere between 10&1/2" diameter and 10&1/8" diameter.
Get a Merc prop. The diameter changes will mess you about as it's not a direct pitch for pitch swap with a Yam prop.
If thats a good 50hp on an SR4, you can swing a 14" pitch merc prop if you're solo.
Need spares,consoles,consumables,hire,training or even a new boat?
Please click HERE
and support our Trade Members.
Join up as a Trade member
or Supporter HERE