Judging but what you have there probably mid to late 90's at some point they switched back to a stamped valve cover from the cast one. Having a mercarb vs TKS, assuming carb is original, would likely put it pre 2008 or so when the mercarb came out (could be of on the year).
Cast aluminum cover is serial 0K9999999 and below
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My current boat is an 0M69xxxx serial - engine was built in 2003 so thinking 0K9999... would be late 90's or a tad earlier ....
you would probably have better luck looking at the casting numbers on the block and seeing if you could research that. usually there will be a date code when it was cast but I have no idea what it would be for the 3.0