parts are available
don't know how bad your engine is or whether you are too late
I have the original engine in mine but don't buy volvo parts unless i have to
The engine under the volvo bits is the Peugeot indenor diesel engine and millions of these we sold in cars and pick up trucks worldwide so engine mechanicals can be got certainly in europe.
I buy oil filters gaskets etc from my local motor factors for a fraction of the cost
ref power. MD21A is rated at 75HP at 5000 revs but the manual notes this is f0r planing power boats only. it is not recommended to exceed 3000 rpm in a displacement boat and teh power output is then circa 60 HP
Most common replacement over hear is a 30-35 HP beta or to replace with a rebuilt MD21A or B.