68H is the specific engine type and the plate on other side of the bracket will give engine number, shaft length and build year if it's still there. That's a 2.6 225 as opposed to the 3.1 Vx 225. Fairly straightforward engine. Not sure but don't think Haynes did a service manual but Marine Parts in Swords may have or could get you a Clymer manual to suit. A user manual should be easy enough to get a hold of, might even have one stashed somewhere, I'll check.
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