So I put this in a previous post but want some input so I figured I would repost. ? Is why do the lower shaft have greasable bearings and not sealed. Sealed bearings are greased for life of bearing and no dirt can get in. I figured a sealed wheel bearing goes thousands of miles before they go bad even at high speeds like motorcycles they ride in mud, dirt, water etc. Why would it matter to use no greasable sealed bearings in your lower unit. *** This is just a topic that picks my brain and wanna hear what you guys think ****
Anyone feel free to chime in and give your opinion or thoughts or knowledge

Quick answer - many MM designs use primative yet very rugged bushings not bearings
on their power output shafts.

Part of the reason I ask i rebuilt my lower unit on a copperhead and it seems that it just traps water no way to "purge" it out also how about double lip shaft seals. So another question say I used just stainless steel sealed bearings and never greased how long do you think it would last til they fail

Backwater uses sealed bearings.