Since my 2 outdrives are on temporary stands seems good time to paint.........no corrosions or pitting just some peeling paint......not painting the lower units of these ssm3's
but would like to clean and polish the aluminum what to use? .......for the uppers was thinking sanding but what grit? ......I have the primer, paint & clearcoat already.

Just my .02, If you have bare aluminum you’ll want to scuff that to 120 grit, any flaking paint you’ll want to hit with 80 then down to 120 for smooth appearance and give the surface something to bond to. Rinse, then wipe all down with IPA or denatured alcohol and should be good to prime. Check your product for coat times, you’ll want to apply the topcoat within the primer allowable paint range.