I have a 94 5.7 MCM Alpha Drive (Serial #OF235240). As you look at the lower unit from the top down, there is a plastic plug on the top/back of the unit that caps a small space that appears to house 1 bolt. A wave slammed the back of my boat into a dock and sheered the cap off. A small piece of the opening also broke. Is this a problem and if so, how big?