Maybe someone was trailering the boat with motor up on tilt levers....bouncing up and down....bent the parts. A $30 Transom Saver will prevent this damage in the future....
A few drops of oil on those moving parts now and then will keep it operating smoothly....as with anything that moves ( like the cowling latches), etc.....especially if you're running in saltwater....
Buy a can of Freeze-Off rust penetrant at Auto-Zone or similar auto supply store....it uses very cold co2 blast to loosen screws,bolts and fasteners.....
Drop lower unit again, find neutral in lower unit by rotating prop shaft by hand and moving gear shift.....put it back together and should be good to go....
I use a light coating of marine grease on both sides of gaskets.....makes everything a lot easier at disassembly time.....in fact I re-use the gaskets when I can...
Most folks will put their shifter control in neutral before dropping lower unit, then shifting the lower unit while rotating prop shaft by hand to find neutral, then they're both in neutral when you re-install lower unit......
We're talking about 50 gallons of water and maybe 8 ounces of muriatic acid.....it will have no effect on rubber impeller, and as long as it's circulated with the motor running it will soften and remove the salt/ mineral deposits.....as mentioned, the heat from the exhaust will help make the...
Run the motor in a 50 gallon drum of fresh water, keep drum full with garden hose...add a few ounces of muriatic acid to drum.....soon you will see salt/mineral deposits being removed in the form of a white/grey colored foam on surface of drum....water in drum will get hot due to exhaust, so...
Probably just a normal 2 stroke outboard rattle....my old C90 makes a few noises that are hard to identify.....guess this is why folks love the modern/quiet 4 strokes.....
I believe these wave washers are designed to be an interference fit on the shaft, making them a bit hard to remove without distortion or damage....then maybe they don't work as designed if re-used.....
Using reverse as a brake to approach a dock seems O.K. To me.....but the engine RPM's at shift would be important to any potential damage to the clutch dogs.....I mostly shift at or very near idle RPM.....say around 750 to 850 RPM's......your operator may have just been " slamming" into gear...
