Just changed the impeller on the lower unit ('74 Mercruiser 302, 5.0 225 hp)had it in gear when I removed it. Changed the impeller put the lower unit back on about 8 times to try and get reverse but nothing works. Test drove it forward is fine, put it in neutral still in gear - I have to ease it in reverse to go to neutral. When putting in reverse engine/ gear doesn't engage and the engine just revs up. The boat is a 1974 Sea Ray 200. Also when putting the lower unit back on should it be difficult for it to slide all the way up or do the nuts supposed to bring it up on the drive shaft. When tighting the nuts, there was a little pop. Tried putting the lower unit on in neutral, reverse, and forward multiple times. Are there any tricks out there that I don't know, or is the lower unit garbage and I have to get it rebuilt or buy one? Please someone help....