Why I didn't think of a small launch straight away illudes me to this day because I've always enjoyed boating activities of any sort. Anyway, here it is and what great fun we had building it, and still have, steaming along in it.
Apart from the engine castings, and raw materials (eg wood, steel etc) everything was home made, boat, engine, boiler, trailer, the lot. Even the propellor was created with a hammer and a welding set along with a bit of imagination. And after a few de-bugging voyages, it behaved perfectly.