Upgrading Engine

[tntitans21399]

I bought my first outboard boat last jan. I love it, but the only down side is the outboard. It is a 1972 Chrysler 55HP engine. I pushes my 16 ft Terry Bass around about 21 mph (by myself), which is fine with me, but if one only person (doesn't matter if it's 1 or 4 more) then the boat drops to a slow I'm guessing 10 mph. I checked the compression and both are at 140. A couple of my friends said with the 55HP that it should be going a little faster. I was going to upgrade and get a newer engine 80's model maybe. I'm not looking to be going 80 mph but if I could go about 20 with people would be nice enough. My question is since it's a 72 model it has the small old prop, and I was wondering how much of a difference a newer 55HP, with the bigger typical tradition type prop on most boats now, would make? If the newer type engine would make a big difference then I might stay at the same HP, but I was also thinking about going up to a 75-85HP. What do y'all think?