I have met coastguards all over the world, and have been one here ...in foreign parts you never try to outrun them no matter what you are in, they are not all as friendly and helpful as ours!! They tend to have attitude and sidearms, plus rifles clipped to the cockpit sides
My friend had 125hp on the back of a 6 metre sportsboat in Turkey and the tax was allegedly around £10 per hp per year. But of course the local mafia hadnt told him that when they sold him the boat. The Mafia solution I believe is that they registered the boat as tender to their bar to bring tourists in from cruise ships and were exempt.
Not necc the Mafia of course....other clandestine organisations are available.