Member on this forum posted his build of a Ramborator kit a couple of years ago,search for posts by Phantom_Maloo. I think you`l find it useful . Motor size 540 adequate ( MFA from Maplins ?)check if suppressors fitted , but better motor mount from Anglia Model Centre, see pics on their ebay site, metal or plastic, splined coupling ends without centre, same place and a few inches of glow engine exhaust silicon tube. etc etc list of other suppliers on Mayhem. Gel cell batteries 6v 4.5amp/hrs from the component shop . co .uk see Maloo`s write-up , he doesn't show finished boat. He was on the forum in last few days, maybe worth a PM to him in Oz . ask him to post a pic of his finished boat. Keep looking for discarded large-ish toy trucks , dozers etc for easy conversion of top.