Call Brian McDonnell http://www.mcdonnellmarine.com/

He ONLY does Volvo Penta, and he's a true master mechanic. He's expensive but amazing in his knowledge. If you're anywhere in New England, he'll make it run right and whatever he charges it's cheaper than a re-power. If it's not worth fixing he'll tell you that also.

BTW my engine was due for a timing belt change so I had him do it, even though he charges for travel and he's 90 minutes away.

I had him take the engine in my prior boat to his shop for a refurb (it had been partially submerged before it got it). I told him to tell me if it should be replaced but he said it could be restored nicely. I trust Brian more than anyone to do it right. It was rusted and looking pretty nasty when I gave it to him, and it came back looking great. It ran like a top since then and that was about 8 years ago, I had it 3 years and the current owner is still doing just fine with it.