Ralph, chances are when it popped out of gear it was because of a maladjusted shift cable.
The Evinrude/Johnson outboards of that size used a lower unit extremely similar (if not exact) an OMC Stringer (800 Series) or an OMC Cobra V6-V8 lower. Basically everything in the lower unit turns as soon as the key is turned with the exception of the prop shaft and clutch dog. The dog is splined directly to the prop shaft with a forward and reverse gear rotating on a pinion, one going clockwise, one going counter clockwise.
This is a clutch dog gear case and chances are it rounded a dog or two. The problem will not simply go away, but rather get worse. Basically because there is now loose metal floating around in the oil.
My best recommendation would be to have it torn down by a reputable shop before the damage worsens, worst case is a new gear set and clutch dog, a long with a seal kit and water pump.
The redneck idea is to change the lower gear case oil and run a magnet through it to see how much metal there is and if not too horrible, squirt in some new oil and perform a synchronization and linkage adjustment on the controls. The instructions are in the manual and should not take more than about an hour.
What happens is the dogs round off and get weak and wont hold things in gear. I would look for a damaged/stretched shift cable.
Good hunting.
GT
