18 cc ?? Not sure, depends on where you want to run it. ANY engine will push a boat through the water, but if you want to run on land, a larger engine is the way to go. It also depends on the size/weight of your boat. on mine i originally had a 20cc weedeater engine, moved fine on water but would not move on land, so I went with the chainsaw.

No, as i said, a pusher prop will make my boat go backward, now if the engine were in a puller type set-up, a pusher prop would be the correct prop.

a chain saw engine spins opposite of ....say....an r/c airplane engine. I hope I didn't confuse you more[&:]

basically, mine is a pusher type set-up with a puller type prop.....prop mounted backward