With only a road map for directions, he set off on the river Medway, from Gillingham, and headed for Southampton. But the RNLI said the man had "ended up travelling round the Isle of Sheppey".
A spokesman said: "This guy had run aground after running out of fuel. He was attempting to travel around the UK from Medway to Southampton and somehow lost his bearings and ended up travelling around the Isle of Sheppey. "He didn't have the usual maritime charts or navigation equipment."
The man told the rescue team he had been keeping the coast to his right and had ended up sailing in circles around Sheppey.
The motor cruiser was towed to Queenborough and officers gave him advice on fuel usage.
Neville Crane, of the Isle of sheppey HM coastguard rescue team, told BBC Kent the man had owned the boat for less than a day and seemed very surprised that its fuel consumption was greater than his car.
You know what this reminds me of? When I was a kid I learnt about the 'hand on wall' method of solving a maze, and I remember being taken to Hampton Court and successfully using this method to thread the famous hedge maze there. It works fine provided that you put your hand on one of the hedges immediately upon entering the maze. But beware if you start the hand-on-wall bit after you've been wandering about the maze randomly for a while! If you put a hand on one of the 'island' hedges (you can see which they are in the map) you will go round and round forever without reaching either the centre or the exit.
Looks like this poor guy did the nautical equivalent of just that.