Hello, I am fairly new to working on boats but been working on cars and trucks my whole life. I just recently acquired a 1988 bass boat with the original 85hp Force outboard motor on it. The issue I'm having is that I'm putting the lower unit on it because it was off when I got it due to impeller needing replaced. The guy I got it from took the lower unit off and never put it back on. So I put a new impeller on and bolted on the lower unit but now the gear shifter rod seems to be too long. It won't go into reverse because it's hitting the bottom of the upper unit,,if that makes sense. I discovered that the rod is threaded and I screwed it down as far as it will go but it's still too long. Is there anything that is supposed to go in between the upper and lower units, like a seal, gasket, or something to take up some space? It's only about a 1/4inch off. The model is 856X8B and serial 4550. Thanks in advance.