1983 90hp evinrude wont stay in gear

[Lonnie5]

have a 1983 evinrude 90hp that will go in gear forward and reverse but when give it more than half throttle it jump out of gear and makes a noise like gears grinding and ideas?? thanks

 

[emdsapmgr]

Either the FNR is out of adjustment, or the clutch dog is worn in the lower unit. Was the lower unit off the midsection recently?

 

[Lonnie5]

what is FNR?? and no nothing taken apart. boat was fine the first two times out and started this jumping out of gear in the middle of the day this time??

 

[BonairII]

FNR= forward/neutral/reverse?