Boat hours Vs. Vehicle Mileage Conclusion

I have seen this posted quite a few times over the years, and it always seems to get alot of reponses on Wakeworld. With that said, I noticed that my 2005 GMC Sierra tracks Engine hours as well as the Mileage (pretty cool feature). At 25,000 miles on my truck, I am close to 1000 engine hours. Now everyone will say that a Boat motor works harder than any vehicle does. Lets assume the average rpms in a vehicle is 2000-2500. Even if you doubled that for a boat (which I think is a bit excessive), you would have to figure that 50,000 miles would equal 1000 hrs for a boat motor. So a boat with 2000 hours doesn't look all that bad (equally approx. 100,000 miles). People are always concerned with Engine hours on a boat. Of course it is how well you maintain your Boat and service the engine. Which brings me to my next thought. The recommendation for oil changes are 50 hours which I have always thought was a bit excessive. I normally change oil between 75-100 hours, mostly because I am not running my boat hard, and spend probably 30-40% of my hours creeping along, enjoying the scenery/Music/Beer/Company. These are not facts by any means, just observations to what I have noticed. Does anyone have a vastly different opinion about Hrs. on a boat motor in comparison?