I would assume its metal flakes in the oil and that there is something wrong.
Are the magnets on the lower end fill and drain plugs still present? and if so what do they look like?
A little bit of filings isn't something to be too concerned about... looking like the magnet is growing a beard of metal shavings is bad. the trick is knowing how much means you have a problem.
Take a sample of the oil to a reputable boat mechanic.
Small metal particles in the oil/ on the drain plug magnet are very normal....larger metal pieces could indicate a problem.....I expect you're O.K. to go!...
If you can see particles there is an abnormal condition. If you still have the oil, take a drop and rub it between your fingers. If you feel "grit" or any roughness you definitely have a problem. Even with normal wear the oil should feel silky smooth.
