I know these motors have a reputation for being reliable, solid motors.

Boat I�m looking to purchase has an �05 200 Yamaha hpdi. Owner doesn�t know hours. No hr. Gauge on dash. Is this motor able to be connected to a computer for hour readout and use at different rpm ranges like a merc is? How many hours is �too much�, to consider, 500 or more? Aside from compression, is there anything else I should have a mechanic look at?

Thanks in advance for any help

Yes, it can be hooked up and get that info and more. I don't think 500 hours would be to many for that engine. A Yamaha mechanic could give you his opinion.

Depends on maintenance,services performed at Yamaha suggested intervals, hours & priced accordingly. I'd rather buy a 500hr motor that was maintained & serviced ( paper receipts & records) than one with 200 hrs that hasn't been serviced & maintained. I'm talking paper here, NOT he says it was. Ask for a printout checkout by Yamaha mechanic. I have a pristine 200 Merc for sale that I ain't afraid to take to a Mercury mechanic for checkout. Im repowering with a 250 Yamaha SHO myself. My boats rated Any V6.
Good luck with whatever you buy & stay safe out there.