flywheel key/new to me 20hp 1985 johnson

Been reading posts about damaged flywheel keyways.What would be indicators of a damaged flywheel key even if only slight damage?Prop has some damage, but I have seen worse. Could an engine run pretty descent, but only have some minor symptoms, such as maybe a slight backfire or hesitation while accelerating and otherwise seem to run strong.Not sure how much force it takes to damage one since the prop is chipped off and a lobe bent at tip.Key stronger than the prop?

normally, engine would not start,timing would be askew, Key is there to prevent catastrophic damage to drive shaft and crankshaft,thus limiting damage to propeller only theoretically. Have seen some engines start with a damaged key,but run a little rough

The rubber hub in the prop is there to prevent damage to the rest of the drive train. Yes, you can still demolish the prop, but the rest of the motor should be OK. Flywheel keys are destroyed by improper installation of the flywheel. Flywheel and crankshaft are usually damaged at the same time.

Check engine sync a flywheel key will most likely be a no run condition. There is a mark on the throttle cam with the engine off slowly go from slow to where the mark on the cam is center of the follower roller the carb butterfly should just begin to open as the line passes center of the roller. Once you get that correct you need to adjust the WOT link. On the link rod that goes under the flywheel is a collar with a screw loosen that screw and put the engine at full speed with the grip with one finger push the throttle butterfly on the carb fully open and the push the collar up tight against the pivot pin and tighten the screw that holds the butterfly fully open.

Get a new/used prop you will beat that engine to death with a deformed prop. I just check my book the roller needs to be inbetween the two marks on the cam when the butterfly begins to open. To get it exact attach a straight paperclip to a alligator clip and clamp it onto the throttle shaft of the carb that tells you exactly when the carb begins to open then in forward gear engine off work the throttle a few times while watching the wire when it just begins to move confirm the roller is center of the two marks on the cam.
http://www.ebay.com/itm/0326876-Pla...ash=item5d6e24d6e7:g:M9YAAOSwx6pYrFOE&vxp=mtr
attached to magneto plate under the flywheel

?-------The same key is used on flywheels from 9.9 to 300 hp I believe.-----------The purpose of the key is to line up the flywheel for proper timing.------------The key DOES NOT drive the flywheel.-----------The flywheel is driven by the tapers.---------------Tapers must be clean / dry / fit properly and torqued to the correct value.

Thanks for the responses.Clearifies keyway questions.My motor starts cold after about 4 pulls and the throttle plate does seem to open when it is or just passing center of two notches on plate.Still trying to feel this old motor out.Hope to get a new prop or have this one rebuilt.Figured the vibration was not good for it.I have been leary of putting any money in this since there was no gear oil in it when I bought it except for acouple ounces of black tar like remains of oil and no idea if anyone ran it this way other than to test it for selling.I have drained and filled gear oil three times to make sure it is fresh.It appears to have no seal leaks.Supposedly in storage a long time?Have used it a number of times and it has great power and has not jumped in or out of gear.

Good luck newyota with your project and safe happy boating this year.