Broken Exhaust Shutter-Does it Matter?

[Woody from CamlachieOn]

Engine is 1995 4.3L Mercruiser Alpha 1 IB/OB, mounted in a 20 ft. Regal Boat<br />While doing end of season servicing, including checking my water pump impeller, the service shop found an "extra" brass part laying on the impeller.<br />The shop found it to be a broken "exhaust water shutter," Mercruiser Part # 99370A-2. There are two of them, acting as check valves on each exhaust manifold. One must be OK. My understanding is that they prevent water from rushing back into the manifold, due to large back swells, or if you let the boat "crash" into the water off of the trailer.<br />To fix requires the engine to be removed, as there is just no room, no how, for a body or arm to get between the transom and the engine.<br />Question: Running without the shutter, and knowing how to avoid the problem, seems better than yanking out the motor. I have two years experience on the lower Great Lakes. Don't want my limited "experience" to get me into trouble. I'm open to advice. Thanks...