I would say in my experience a skid-steer is the most abused, neglected piece of equipment you will find on a jobsite, many times they are made to do a job they are not designed for but people keep pokin' and proddin' till they finally get it done, 2000 hrs. on pumps and motors eeeehhh, could kinda go either way theres not a cut-off point to say like with 1999 hrs. the pumps are still good then with 2000 their bad I've seen them with alot more still going strong but I've also had to rebuild them with less, it goes back to the operating and maintenance issues, its the same deal with the cracking boom arms with one exception I'll get to in a minute, I too see alot of boom arm cracking and can only attribute it to age and abuse they are too strong for their own good, be wary of an 873 B/C that has non-factory welds and patches on boom arms they have a new style arm for the 873's that I haven't heard of any problems with. As far as engines to avoid I dont know if any other manufacturers use it but B/C messed up once and put a Peugeot diesel in a machine (751) theres not many of them out there but beware of this you dont want one of these.