quote Bullie:
I imagine I can figure this one out but am I on the right track thinking it is probably the clutch dog?
Yes, it could be the clutch dog and/or the forward drive gear, but before you tear into the lower unit please consider evaluating 2 things.
1.) A broken shear pin
2.) Remove the face plate on the exhaust housing that allows you to access the brass connector to the upper and lower shift rod pieces. Inspect the shift rod connector to see if it has be striped or improperly been installed. This could cause the lower unit to pop out of gear.
Just a few thoughts prior to jumping into the gear case. If the water pump was service recently, then it maybe shift rod connector improperly installed.
Good luck my friend!
Cajun