I flushed the gear oil out of my lower unit and replaced the impeller. After I bolted the lower unit back up and checked everything out, I don't have reverse anymore. It shifts to it but now the prop is in neutral. I removed the lower unit and checked the shift linkage and sure enough, when the linkage is in the 'reverse' position (all the way down) the prop shaft is not engaged. I pulled the propeller shaft assembly off the lower unit and everyting looks okay, but it appears the clutch or 'dog' doesn't throw far enough now to engage the reverse gear. I know older and smaller outboards were available without a reverse, but this one definitely had one yesterday and I don't have any extra shims or washers left over. Any ideas on what I broke?