My boat is an Express 1870, aluminum, all welded, a very slight V deadrise of 6 degrees at the transom....mostly flat bottom. The boat/motor package came with a 90 HP Yamaha....it's always been for me a bit more power than I generally use...will snap up on plane quickly and plenty of speed.....but honestly I believe a 70 HP motor would be more than adequate for my boat. Of course it would all depend on how far/how fast you're wanting to go....Another factor is that flat bottom skiff type boats aren't all that good for high speed, since they can tend to porpoise if trimmed up for speed.....good luck!