I took my RIB out for the first time today and everything went good. When I got home and started cleaning out my RIB. I found this fluid leaking from the lower unit. Any thoughts on what this is?
I presume you mean the creamy-white substance running down the lower leg?
I'm not familiar with your engine but I believe that the screw it's running from is probably the lower unit oil fill. Could be that it wasn't fully closed and oil has been pushed out when the engine was in use.
From the looks of it the gearbox oil is emulsified with sea water too so you'll need to change the oil as soon as possible to prevent any (further) damage. This happened to yammie 50 i had a while back.