The average running time for a pleasure boat is about 50 hours per year give or take 10 hours.
If you fish a lot like me you can pile up the hours real quick
I/O VS outboard. Out board is easier to maintain now. I/O especially used ones can be a hassle. There is more to go wrong on a I/O beside the lower unit. Risers for one which can add up, but run quieter. The reason I say now for O/B is that the newer engines will meet the 2006 standards put forth by the EPA.
These restrictions have to do with the amount of emmisions put out by an outboard. After 2006 there will be no more carberated O/B engines sold. Everything will be 4 stroke or something like I have which is the Yamaha HPDI series. ( high pressure direst injection). These engines do not shoot excess gas or oil into the water.
I have seen them run in a tank and after running awhile there is no slime on the water or the tank sides that a carberated engine will leave. It is preety amazing when you think about it.
But when you have to have it fixed it will be more complex.
You have 4 years to worry about that though.