The next time you're thinking of it while on the water, with your normal load, get up and go to the back of the boat, as far back as you can. While you are standing there, look at how low the boat is sitting in the water. That's what it's going to look like with a 90 on it before you even step foot on it.
The 75-90 horse engines are all 4 cylinder, and most are at least 150 lbs heavier that the 50-60 hp 3 cylinders. On a 16' low profile bass boat, one that's not real wide, this is a big deal.
I set one of these Tracker Pro Guides up with a Honda 50 not too long ago. I was pretty surprised when had to back off to a 13 pitch prop to get it turning up into it's power range, and then it would only go maybe 25mph. That boat was a dog as well, but being as it was an older one (1998), I was thinking water logged foam was the issue. Maybe it's not....
Bottom line, there's no way on God earth I would put a 90 on this boat, I don't care what it's rated for. It will be sitting very low in the back.