A SeaCraft 18' and a SeaCraft 20' are only 200#s different in weight. I've owned both simultaneously and any engine that will push the 18' will do just fine with the 20'. I've had three different engines on those two hulls, two 140's and a 130hp.
I was pretty pleased with my fuel consumption before the current spike in gasoline prices. I'm even happier now that I went with the engine that I did (currently a 140 Suzy). Other people may get there faster than I do but I do it for a lot less
