great engine, arguably one of the best mercury built... It is based on the 2.5liter block, and 175hp is the lowest it was ever rated at. (meaning the block is very overbuilt for 175) Earlier years (pre 98 or so) did have issues with the oil injection pump, it was generally fairly reliable after that, and if you are worried you can always just convert it over to premix.
Things to watch out for... Ask them if they have changed the stator and lower unit oil. Both should be changed yearly, and people sometimes forget about it, especially the stator. When you look at it, take a flashlight and crawl under it, look up the intake and see if it is beat up. The impeller is a cheap fix, but the wear ring can be a little expensive. A quick fix that I've done on all my jet boats is to build up the wear ring with jbweld. Surprisingly it lasts very well, a couple of seasons at least.
Finally, those merc 175 jets can be a bear to start cold, so don't take that as a negative sign when you look at it. They have no anti-drainback valve and no hand primer bulb you can pump. Merc put a bandaid on, in the form of a primer pump that runs when the starter is running. Only problem is that you have to grind the starter away while the pump is sucking up fuel, and that is even if the pump is running, since the starter is dropping the voltage. I've got a quick fix posted on a different site that allows you to run the primer pump manually with a key-switch, it makes a HUGE difference.
http://jetboating.net/jetboating/common/articles/display.aspx?id=96
