Re: what would be a good engine ?
You have to be a little bit careful with four strokes. They are heavier, horsepower is one thing, weight is crucial too.
Basstracker was/is notorious for putting marginal power on their boats to keep the package price down.
Look around, on your boat for a metallic tag that is yellow and silver. That tag will have the max. HP rating on it. As I recall, the TX series (17 footer) Trackers were rated for 75 max. A 75 Four Stroke would be far too heavy. So would a 75 e-tec for that matter.
A 50 or 60 e-tec would be perfect for that boat. I might go with the 50 since it basically the same engine as the 60, yet far cheaper. By all means, go the 60, if you can. It weighs the same. Plus, either would run rings around that older Merc. "Classic" 45.
That old Merc. has some value. They were very smooth running engines. Many folks desire them.