Hi! I have the same boat.
If the wear rings are bad, I would guess it has been in salt water. I boat in fresh only, so can't really say whether that is at the right time or not for that issue. I do know that the salt water corrosion will swell the ring and cause it to contact the impeller, causing issues. That said, a pretty easy fix.
Impellers: Mine were dinged up pretty bad about 1.5 years ago. I pulled them, filed them down, put them back in. It made a world of difference. Don't know if that would work for the one you are looking at or if it is worse. Impossible to tell without pics, but just a thought for you.
Compression: Normal compression, I'm told (on this site) is about 135 per cylinder. So it sounds like all of yours are in range, but that is a pretty big swing to me. Doesn't sound like a problem...
Full service: Full service on mine at the dealer was $450. Plugs, grease the intermediate bearing, and change the oil (2 engines). I thought that was a ridiculous amount for that. I never went back; I invested $40 in an oil sucker and have done everything myself since then. That means they are charging you like $1500 to run ring free in your engine. That sounds insanely expensive.
Upshot from my perspective: I would be interested what others would say, but I don't see any red flags here as to the boat. A red flag as to the dealer.... But, yes, you may have an indication of early, early issues on the engine--but probably not. I haven't done the compression on mine but I would not be surprised if mine were similar. And mine runs fine....
My 2 pennies. Got pics of the candidate?
