Sorry for my ignorance guys, new to the older drives as I've only had experience with Bravo applications. Have an 85 12 meter fountain that I believe has SSM #3's on it, 1 1/2" prop shafts, 19 spline- #3's correct? I could'nt see a drive ratio stamped into the upper, I assume 1.5:1? Just took the props off to see what props were on it, 16.5X24 4" hub. Noticed the the starboard drive was missing the black outter prop shaft seal? Boat hasnt ran in na few years and were are putting new power in it, 540 ci n/a shooting for around 675 HP with a little over 700 tq. What kind of HP ratings are these drives ok up too and does anyone know what seal that may be? looking at the merc diagram I only see pt# 26-19473 but that doesnt look like a black rubber shaft seal? Thanks for any advice or comments you may be able to provide. MIKE

Those are 3's. The ratio could be 1.33:1, 1.48:1 or 1.58:1, mercury rates them for 700 hp.

Thanks, any idea what that outer shaft seal is? Part #? and does it just slide over the prop shaft against the housing or does the shaft need to come out to be replaced? Thanks for any help guys, appreciated. MIKE

https://www.mercruiserparts.com/Show...+%28III+SSM%29
Propshaft and seal look like they go in from the back

Thats what I thought looking at the diagram but this is what that seal looks like, pt# 26-19473. Not a black rubber oil/water seal? Or am i wrong?

Call Galen at Speedmasters in FL. He can tell you about the 3's and get you the part.

Wannabe

That looks like an oil seal to me, not sure I follow you