There is little you need to do to maintain a modern 2 Stroke 40hp Outboard Motor — but what is still needed is vitally important. You can blow up an engine by neglecting its cooling needs, clog it up by ignoring potential fuel problems, bust it up by letting the lower unit sit over winter with leaky seals. Depleted zincs can invite corrosion. Dinged props can shake the stuffing out of bearings and other moving parts.
Owners manuals have slim maintenance sections. That doesn't mean they're unimportant.