Hello,
Any help would be appreciated. This is all new to me.
I replaced the impeller on a mercury 3.3 hp but it seems too big to fit in the housing and not sure how it will turn.
Also, when I reassembled everything and got the motor running, the prop is now not turning and my forward and reverse is locked up.

Thanks

You will need to take off lower unit and realign mate shift rod correctly.
In order to get it back correctly you will to put the shifter in reverse as well as the the lower unit (Prop).

You can use pliers but, be careful not strip the gears spindle on the lower unit w/(Prop).

Take something small like a paper clip to help you position the shifter down rod up in place before you slide the lower unit back into place. You need to focus on the the lower gear spindle to make sure it mates with upper down rod.
I find it easier to spin the prop as your pushing it up into place. Two people usually works best, but I have accomplish this myself on a 200HP Merc.
I hope this helps.

Thanksfor your help. I'll give it a try.