99 225 johnson problem

[bryce miller]

i have a 225 johnson and it has a knocking noise i think in the lower unit. you can put it in neutral and rev up the engine and the knocking stops, you can put it in reverse or forward and it starts knocking again? any ideas what it could be?? thanks bryce

[THE WITCHDOCTOR]

I think I would check compression and such first, then move on to the lower....