how much schould a valve job be for a pair of 525scs and is any mercruiser certified mechanic qualified

I doubt the Merc shop would do the heads themselves. Find the best head shop in town and ask your mechanic to send them there.

The expense of $175 to $250 for the valve job, thats facing the valves and grinding/cutting the seats, is not the kicker, the kicker is the R&R of the cylinder heads by the boat shop. While apart I would check spring tension and valve guide wear.

Chris

Im located in upstate NY Albany area

Hugeld-- you don't say how many hours are on those heads/last valve job. You might just want to change the valve springs. It's a lot easier now to shim/set-up the spring heights after the valve job. As Chris said, check the guides for wear before you spend money on the valve job. Probably not a concern, but check the rockers for wear too while it's all apart on the bench.