....On NO account buy another Volvo to put in there. Volvo engines have a competitive price new, but the spare parts are shockingly expensive......
I'm not going to dispute the ultimate conclusion. I have a Volvo and, if I were repowering, I would switch. However, this would be based almost entirely on the access to Yanmar technicians and parts inventory. I have purchased my share of spare parts and haven't found them to be significantly more expensive that other rip off marine parts. If one really wants to reduce cost, one of the converted tractor diesels is probably the way to go. Then buy your parts at Napa.
I suggest that any 20 year old engine from any manufacturer has at least the potential of requiring an expensive part. It depends on how long it has been since they made the model, than how old one's particular motor may be.
I'm not a big Volvo defender, but they are generally reliable diesels and are very common world wide. In my case, the 100hp Volvo runs significantly quieter and at lower rpm than the equivalent Yanmar. I like that.
If one shops for parts on the internet, you will find much better prices and your local dealer may not even what you need at all. If you even have a local dealer. One of the more significant mark ups on all parts, is inventory carry. The cost of money for all that inventory sitting on the store's shelf until sold. With few Volvo owners, parts sit longer. More mark up. The internet providers get some of that economy back.
I'm just saying there are two sides.