I just checked the length of the propshaft thread and its 12mm, so if you are using a drive dog on your propshaft then yeah, you are going to need to buy some threaded props.
Curly would have sold you a motor around the 3000kv range, so get a prop around the 30mm range. IT MUST BE A THREADED RIGHT HAND M4PROP!
Here is a link to where i buy mine, i get the 31mm RH M4:http://www.cornwallmodelboats.co.uk/...rs_2318m4.html
About the water in the leg area.....just cut off her big toe, it lets the water flow out if any gets in.
I honestly have absolutely no idea about what you are thinking i am soldering, but i will try and give an answer.There is a hole in the propshaft tube where you can fit an auto re-greaser to the tube, but given the little amount of space inside the board, you need to seal it or grease will fly out. Sealing it with solder seems to be the only way to keep it sealed. And yes, a right hand prop will tighten as the shaft spins. Saw the pics, Spain does get some waves, the west coast is much better. I suffered the smallMediterraneanwaves off Mallorca for a long time.