I have two boats at the moment. The first is a Dickie tug conversion. This has an oiler attached to the tube, filled with normal car engine oil, ( as per the prop shaft manufactures instructions ) runs smooth as silk and no water gets in, not bad considering the whole tube is below the waterline. Yes, a TINY bit of oil might leak out but the lake i use is full of duck / seagull crap and feathers, does it reallly matter? My second boat was just a normal tube that i filled with grease. Bad move as the 400 size motor slowly wirred into life you could just tell the grease was slowing it down. This has now been ripped out and a prop shaft tube from Marks Model Bits is being fitted. Stainless shaft and tube, PTFE bearings. The bearing at the prop end will be water lubricated and just a smidgen of grease in the tube at the motor end to lubricate the bearing and keep the water out. Not run this type yet but it looks good to me, regards, Dave.