Depending on the configuration of one's wet exhaust system, cranking an engine without starting it could lead to overfilling the wet elbow/muffler with the result being backing up some water into a cylinder or two.
While I don't believe in cranking on the starter to lube a regularly used engine's innards, I also suspect Ski's assessment is correct in that it probably won't hurt anything enough to be the cause of an engine needing an overhaul.
So if one chooses to do this, they should make sure that pumping raw water through the boat's cooling system with no exhaust present to clear the water will not cause any problems.
While I don't believe in cranking on the starter to lube a regularly used engine's innards, I also suspect Ski's assessment is correct in that it probably won't hurt anything enough to be the cause of an engine needing an overhaul.
So if one chooses to do this, they should make sure that pumping raw water through the boat's cooling system with no exhaust present to clear the water will not cause any problems.