TOPIC: 1967 mercury 50hp prop shaft seal

i have a 1967 50hp ser# 2118477 that i am replacing the prop shaft seals in the bearing carrier and i want to make sure i get the right part. this lower has the smaller 3/4" shaft and i am coming up with two part numbers 2623517 and 2690562. anyone know which is the correct one? i tried using the lower from my 1974 65hp parts motor but the studs near the water pump are in a little different position.
thanks
steve d

I'd go to NAPA and buy a Sierra Marine 18-2011 and if it doesn't fit take your old seal or the related measaurements to a bearing & seal outlet and get one that way.
If 18-2011 is wrong just contact me and I'll buy it from you.
Thom

thanks thom, my local west marine is ordering one for me. i noticed that this lower unit has a different gear ratio than my 1971 50hp and the lower unit i have from the 1974 65hp is the same as the 1967 50 hp. is one ratio better the other?
steve d

the 1971 has a 2 to 1 ratio and the 1967 has about a 1.6 to one ratio.
steve d

i picked up the seal over the weekend and that is the correct part number. thanks alot doc!
steve d.