I've told this story a few times, but it bears repeating. If you have log exhaust those flappers are a good idea to keep them in place. If you're beached and wakes are hitting the back of your boat water can run up through the exhaust over the risers getting water into the open exhaust valves. Milkshake. It's happened to me. I also made the mistake of coming into shore a little hot, shut down and the water rushed in the same way. Milkshake. IMO flappers are an inexpensive necessary boat part.
Good looking boat, have fun.