Re: 1100SS Lower Unit - interchangability
Any Inline Six lower unit from around '65-up will work. Later L/U's are better. '79-up Inlines came with a redesigned gearcase and swept-back fin and are real nice. I had one on my '71 1350 and it worked great.
L/U's from 4-cyl 66-cubic-inch models 65hp, 75hp, 80hp, 85hp will also interchange. Some 65hp models have a 2.3:1 gear ratio as do all of the other 4-cyls mentioned. You'd need a prop with about 2" more pitch. If you're skiing or pulling tubes, etc, this gear ratio works well as you can swing a larger diameter blade at a lower prop speed for better hole shot.
Newer L/U's don't have an O-ring groove below the driveshaft splines. You could use one of those if you ground a groove in the appropriate place. Or, be sure to remove the lower unit periodically to inspect and grease the splines. If you don't do that, water will get in and rust the crankshaft splines.
You could also pull the powerhead and press into the crankshaft one of the newer-style seal assys that go with the "no-groove" driveshaft, but that's a lot of work!
Driveshafts are not readily interchangeable on these, you'd have to completely disassemble to swap 'em out. And they're not all necessarily interchangeable even if you get one out of the gearcase to swap. They have different sizes of splines on the pinion end, and different types of driveshaft ball bearings (straight, tapered with bearing race on the bottom, tapered with race on the top), so to swap driveshafts you'd have to have one from the same style lower unit.
Best bet is to find a parts motor on your local Craigslist. There are a lot of L/U's on eBay but they're not cheap!
HTH & G'luck..........ed
