Hi - You probably have found the engine and solved all problems by now, but there is a minor cautionary tale for Tohatsu 6HP 4 stroke petrol outboards in Kingfisher 20+ wells. We had one and still have, but found that if it was kept in the "propellor up" position when not in use for lengths of time (1 or 2 months), that is with the engine head tilted towards tthe rear of the boat to lift the propellor up, oil from the engine sump slowly found its way past the rings on the cylinder heads into the firing chamber. This in turn meant that it was very difficult to start, as the oil in the firing chamber rapidly fouled the plug when the starter line was pulled, and that when started the engine produced a smokescreen sufficient to hide the Bismarck, for about 10 minutes, as it burnt off the rest of the oil. The longer the period it had been hinged backwards for, the worse the effect.
The master mechanic who finally found out what was going wrong (after three others failed) said that the engine well had been originally designed for 2 stroke engines, which did not suffer from this problem as there was no permanent pool of oil in the sump - the necessary oil to lubricate the pistons came from the oil mixed in to the fuel. He thought that the problem would apply to any make of 4-stroke motor, if left with the head tilted backwards to the degree used in the K20+ well. The effect only does occur after 6-8 weeks of tilted storage, and the engine does atart very reliably when left vertical in the normal working position. Apparently 4 strokes are designed to fit on normal outboard brackets at the rear of boats, when they are tilted by bringing the head forward and the leg backwards, which keeps the oil in the sump clear of the piston rings, not the other way round.
We have adapted by lifting the engine out at the end of the season, and storing it in the correct position as detailed in the handbook, and leaving it vertical with the leg in the water during the sailing season. Problem solved.