launch at jacks again

just got back from launching at jack's house again. nothing improved. i moved the rudder down so its mostly in the water but the travel is way way way too small to do much of anything. the same problem persisted with the drive. it just can't handle the motor spinnning fast at all. it fails at 4 or 5 notches of throttle. its the same as the first time we tested at jack's pool. so i don't think we've learned anything at all. its very discouraging. my dad suggested getting different pitched scews to put greater load on the motor and maybe slow down the spinning and push the boat more. its a good idea i suppose. and its the second to last resort before i have to go gear the whole thing. the last shot is to get a rigid motor and shaft and see if that works. i don't know, i'm discouraged. i have to order the real boat soon or there won't be any time to start work on it. but i don't know how big a boat to be getting. ARRRG!