Re: Outboard Engine Weights
Dry weight on that 89 50HP is 188 pounds according to my sources. That makes for a hefty weight difference between the 50 and the 175. From what I've been told, the max hp of a boat is all about weight and manufacturers are somewhat generous in their max ratings. It's a marketing point...
You can put the max rated motor on a boat, but you generally get a little better performance with something at about 2/3 or so than the max rating. You lose a few mph, but you run more efficient because there is less weight bogging the boat down. It also frees up some available weight capacity for carrying people or gear.
You should be able to get hold of the manufacturer of the boat to see what the max weight, person, and HP capacities are. That'll let you know how much you can really drop on there.
Either way, if you do put the 175 on there, you should consider shifting some weight to the front to balance things out.