Re: yanmar vs yanmar?
There are lots of Yanmar "sailboat engines" installed in power boats. There is nothing specific to sail or power in an engine. If you need 30 hp engine for your powerboat, then buy a 30 hp Yanmar.
FWIW the small, normally asipirated Yanmar diesels last a lot longer, often 10,000 hours or more without major work, than the high horsepower, turbocharged, seawater aftercooled "power boat" engines.