Given that the RYA have powerboat levels 1,2 etc I'd be inclined to think anything primarily designed to be driven by an engine is classed as a powerboat.
Mine was second hand off a BT van, similar story. Worked fine for a year or so then wouldn't fire up. Servicing engineer reckoned it was badly choked with carbon.
Aquador 28c might fit the bill with two separate cabins, a bit short on outside space though.
https://www.boatsandoutboards.co.uk/Motorboats/aquador-28-c/257613
I had a similar problem with my Matsutec, tried resoldering the pl259 etc without result. After a full system restore I found that the unit had 'lost' my MMSI number, supposedly impossible. Reprogrammed the MMSI, job done, no problems since.
More aimed at boats for angling but loads of good info/terminology in the free book available for download on the link below.
http://www.boat-angling.co.uk/free-downloads/
Well, sort of.
Until you want to stop, or park, or navigate a busy area (no road lanes and even less boaters know the 'rules of the road' than drivers) .......
As others have said, get some training, PB level 2 practical, dayskipper theory. And don't forget to factor in all the safety gear to...
Bu&&er flies over my house every morning, noisy s0d! And Jim Melon who owns the ‘mosque’ but lives in the Balearics. Someone could afford to build a marina in Port Erin for me!
Perfect deep water harbour, especially with these north easterlies this year.