Roller bearings are noisy by nature. They need a tiny bit of clearance to survive, and they do not have the large sheet of oil between them and the shaft. Plus, most OMC motors have a considerable amount of piston slap due to the pistons being tapered by design. If you suspect looseness in the bearings, remove the spark plugs and stick a screwdriver in the hole to follow the piston on the downstroke as you slowly rotate the flywheel. Stop rotating at about midstroke and give a push on the screwdriver. Looseness will show up as a clunk.
Actually, roller bearings do not wear in the normal sense. But they do experience damage from water ingestion. Then they make an unmistakable sound that I describe as like an old steel roller skate wheel on the sidewalk. That is if anybody remembers those old roller skates.
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