So for the moment I’ve got everything working as it should on my boat. Merc 5.0 mpi with an alpha one gen 2 behind it. My question is that at low rpm in gear the boat has a slight vibration to it that goes away with a little more rpm. The drive is a new sei marine unit but I’m pretty sure it did it with the old unit before I replaced it as well. Tried a couple props too. Currently running a revolution 4 in a 15 pitch. Looking over everything I noticed the plastic shins are not and probably never were there since I owned the boat. Could these missing be cause for concern or a reason for the vibration? Also. Looking online I can’t tell if they are the same for the bravo and alpha units. Can someone help me find the correct ones?