...once in a 22 sqm Skerry Cruiser, a boat of similar size and design.
Volvo had at that time (1982) a small petrol inboard with a saildrive. The engine might have been called MB2. It was based on a Honda outboard with a power around 7 Hp. It was a very light engine, not much more as an outboard of similar power. I simply cut a hole in the hull just aft of the keel and bolted the engine bed there.