What do you have for electronics. If you have a digital package it should be a matter of looking through menus. Chart plotters and fish finders have the capability if you have everything tied together through NEMA.
I'm guessing something like this is easy enough, no??
Yep that's the easiest route. I have one of these on my standup. If you're going for a traditional hour meter, you just have to splice the positive lead into the purple wire coming out of the key switch and find a good ground nearby. They also have many tach meters that have built in hour meters where it is a drop in replacement with no additional wiring needed presuming you have traditional analog gauges
https://www.amazon.com/Docooler-Inductive-Marine-Motorcycle-Waterproof/dp/B00A43PKOE/ref=sr_1_3?ie=UTF8&qid=1524512187&sr=8-3&keywords=hour+meter+for+outboard+motor&dpID=41kqI%2BNf%2BLL&preST=_SY300_QL70_&dpSrc=srch
Says you just loop it around one of the spark plug wires. "Inductive"