Farymann 2cylinder 20 hp diesel, parts help

[Cannon]

I just recently bought a small french sailor cruiser 6.67 metres long wooden built, there is a fair bit of work needing done deck etc, but my first item on the agenda is my inboard, it looks like it needs some attention although it sounds okay and no tell-tale smoke probs, the person i bought it from was a french man and for the little french i speak i think he was telling me it is now difficult to get parts for these engines as they are out of production, can anyone help on this one???

And if i have to replace the engine has anyone any recommendations, should i go a bit bigger that 20 hp for example the boat is 3 tons.???
Would appreciate any help.