I would DEFINITELY go with the 9.9 over the 8, especially in your situation, being underpowered due to lake restrictions. It is the same thing you will notice with the Johnnyrude 9.9s and 15s for a long time. Same block, same bore/stroke etc. Differences in the carb and exhaust are usually what equate the difference. They still have to put out the right hp, or they wouldn't be sold, due to NMMA or BIA regs (can't remember which), so you are getting the right hp. Sure, it is only 2 hp, but think about it, if you get the 10 over the 8, it is a 25% increase in hp. And, it is an increase in hp, without the increase in weight. Now, I can't justify getting a merc, or getting a 4 stroke in your situation, unless you are in the areas that don't allow 2 strokes, or do a lot of slow trolling, but in your case, that would be my decision.