I keep three 4,5,&6 Hp Yamaha two-stroke long shaft outboards going as part of my local sailing adventures. All three powerheads have been rebuilt in my dimly lit bug-infested shed from time to time, and all three have gone underwater from time to time, and suffered so many indignities and mix-and-match repairs that I truthfully do not know which is which, but there is always one hanging on the transom. Parts? Piece'o'cake off the web. The exception, shear-pin propellers have gone the way of the dodo, so I change the final drive pinion to the type that will accept the dratted rubber hub type (not a Wave Runner issue). Use NO ETHANOL gas and real good 2-cycle oil (Mine all are 100-1 mix. A teentz more won't hurt)
The Yamahas run as required, and when they don't, which is rare, well it is a sailboat and the prevailing wind is a westerly that blows me home, so all I really need is power to get out, as long as Wave-Runners don't wake-blast me in narrow channels!
Keep in mind that "A teentz more" will lower the octane rating of the fuel and can lead to preignition and piston damage.
I've seen more than a few pistons with the crown holed from careless mixing.
brass rod is a cheap source of shear pin material. I have an ancient 7.5 hp air cooled outboard and shear pins are produced with brass rod and a saw.
Bolt cutters also work but sometimes the ends need a bit of a touch with a file if the shaft hole is a tight fit to the rod.