Prop Question
 

If you bought the engine new, then your dealer will set it up for you. That is a requirement per EVINRUDE is that all engines are setup by the dealer BEFORE they are registered and a warranty issued. EVINRUDE lost quite a few etecs early on because of improper setup(mostly propping), so they now require the engine to be setup by an authorized dealer. If you bought the engine used, then you need to be pretty critical with your propping of it. What kind of prop depends alot on the hull type and your useage of it.

ALSO the jack plate will add absolutely NO more force or stress to the transom.... The force comes from the prop and the mathematical lever arm is exactly from the prop to the top mounting holes in the transom and the fulcrum is the lowest contact point of the transom

You could have a 20" motor or a 120" motor w a 100" jack plate and the leverage would be the same

Now a 25" motor on a 25" transom on the other hand WOULD apply more leverage to the transom than your setup. ..
You are worried about a nonexistent issue.... Forget the reenforcement plate..... Instead just look at blocking water... MUCH less strength needed for that.... Plastic would be my choice

What about prop type?

Aluminum I'd stainless steel?

Spares?

Minimal difference in performance .... Stainless is tougher but aluminum is cheaper.

FERM and smoke do have valid points.

I normally carry one of the spare props I have tested previously, not to mention the stuff to install/replace it with, all the way down to the thrust washer.
The prop composition usually depends on your habits, I happen to like the stainless.

Other spares also depends on your habits. I usually keep a spare portable bilge pump with alligator clips and hose connected, spare drain plugs, fuses, oil, anchor/rope, one more safety vest and throwable than needed. If offshore fishing or camping or riding the grandkids around there will be other things added to the pile of stuff.

Depending on what your jack plate setback is and how you normally load the boat, you might need to raise the engine yet higher than a regular transom mount. A 5" setback might need to go up 1 or 2 bolt holes, a 10" might need to go up 2 or 4 bolt holes.

If you don't have a prop already, I'd expect to start out with about a 15x17" stainless and go from there. If the engine is setup correctly and depending on your habits you might need to go to a 15" or 19" and/or anything in between. This is where a dealer setup situation will save you time/money and get the best performance.

Before I would make a remondation, I would need to know what you're boating is. If you run shallow or an area with alot of obstructions, I'd go aluminum(props are cheaper and easier to fix than lower units). If you are after max performance then stainless is your prop. And how you are going to use it will dictate which style and brand I'd reccomend. Theres dozens of styles of props out now, each for a different useage. Its not the olden days where your choices were just stainless or aluminum.

I run a stainless 14 3/4 X 17 Solas and am very happy with it.

I run aluminum props for this exact reason

I will be running it mostly in Long Island Sound (deep water zero visibility). I may pull it to the Florida Keys (very shallow/good daytime visibility), and occasionally up to the Georgian Bay and French River in Ontario (rocky bottoms, clear water/good daytime visibility). I bought this boat originally because I wanted a trailerable boat.