Originally Posted by
MudPie
Good to hear it's freshwater. Money-wise, it's probably best to use marine grease in the bearings and after you remove the craft from the water, perhaps spray the chain, cogs and other unprotected surfaces with WD-40 or Boeshield T9 to displace the water and add a thin protective film.
At worst, you might get surface rust, but I highly doubt the corrosion will be severe in the time frame you describe.
I commute in winter and often ride through slushy, sloppy, wet, salty brine, and for the last bunch of years using WD-40 to spray down my chain after a good rag wipe to get grit and as much water off after each ride, has been surprisingly successful in keeping the chain rust free.
Not the same total immersion thing, but its just an easy solution to keeping a protective film as noted on stuff, and of course doing the WD water displacement job. As noted above, never hurts to spray other stuff also post immersion after a wipe down.
the bottom bracket bearing is probably worth packing with grease as mentioned, but if it is not a ball bearing type bb, I guess just remove the cartridge bb and grease the heck out of the threads and everything--although as someone else noted, he'll probably be preoccupied with all of the actual designing, constructing and problem solving issues along the way, so if the mtb drivetrain is working, grease replacement and stuff will probably be pretty low down on the priority list.
I'm sure it will be a fun project to work on and try to minimize all the gearing friction points to get as much leg power to the prop