Older aluminum brackets are designed for 2 stroke engines. Manufacturers say there is a big difference in torque between a 2 stroke and newer 4 stroke engines. In my experience, my 4 stroke 5hp engine has been doing fine on a Garelick aluminum 2 stroke bracket. For small boats, with small engines, I have to believe that torque isn't that big of a deal. For a 17' boat, you would probably be fine with a newer 4 stroke 2.5hp engine. When you start getting into the 4-5-6 hp range, they are pretty much all the same single cylinder powerhead, with de-tuned carburetors to lower HP output. So the weight will all be fairly similar.
There are some differences in need of power. People think that if they buck currents, they need more HP. However, if your motor is capable of driving your boat to hull speed (for the sake of argument on a 16' waterline, let's say 5 knots,) to exceed hull speed requires considerably more power. Much of this power is bled off by the bow and stern waves increasing in height (amplitude) because the waterline length holds them to more or less constant max speed. (Wave speed is a function of wavelength, not amplitude. Longer wavelength equals fast waves, so that's why longer boats sail faster than shorter. For a very simplistic explanation.) So, more power means the displacement hull will sit down between bow and stern wave, rather than go very much faster. As an example, towing a one design displacement hull to a race start can have the transom sitting down so low it is almost under water due to the stern wave and the tow holding the bow up. OK then, given the above, if your 2.5hp motor pushes the boat to 5 knots on flat water at 3/4 throttle (assumptions, bear with me) and you know that you normally buck a 2 knot current, even increasing HP it will be difficult for your boat to exceed 3 knots over ground against that 2 knot current, because your wavelength is actually making 5 knots through the water.
More power can be beneficial dealing with wind (up to hull speed) because the wind is so much less dense than water, it is easier to overcome the windage of a sailboat.
In my opinion, many small sailboats have more HP than needed because small outboards are sold with a factory spec "speed" prop designed to run a small planing hull boat like a jon boat at higher speeds over ground while on plane. For our displacement sailboat hulls, a large difference in power can be achieved by replacing the stock prop with a "high thrust" prop designed for your motor. It will have larger surface area blades, so called "elephant ear" or "Mickey Mouse ear" blades, to grab and throw more water. It will also have a greater diameter than a speed prop, again to grab more water at lower speeds, as well as a lower pitch. Lower pitch is like driving a car in 1st gear vs. 3rd gear - more torque, less speed. Lower pitch runs higher prop RPMs, and the motor will be able to run at higher RPMs, which allows a better heat range to reduce plug fouling. And with the higher thrust prop, you will find better reversing, and slowing the boat by shifting in reverse, as the prop moves more water.
The Honda 2.3hp motor is very popular on smaller boats. I can think of 2 Precision 185 boats in my marina. These motors are also easy because they used to be air cooled, eliminating maintenance hassles of replacing water pump impellers. However, I haven't been able to find high thrust prop options for them.
The ubiquitous Tohatsu motor in 4-5-6 hp does have a high thrust prop option - I put one on my 5 hp Nissan. I say ubiquitous, because Tohatsu makes motors rebadged for Nissan, Mercury, probably Evinrude, and possibly one other that I can't remember.
Hope some of this helps.
