2004 Tohatsu 15hp 2-stroke looking in decent condition. As a 15hp it's a little bit heavier than the standard Mercury/Mariner/Yamaha models but very simple upgrade to an 18hp which was 99.9% the same engine. For £1000 BIN or best offer that's cheap.
Have to correct my post above. It's the Mercury super 15 version of a Tohatsu that can be taken to 18hp. As Loco points out the Tohatsu 15 is a smaller capacity engine... which then makes it damn heavy for a 15.