By the time visiting family had left today it was too late to jump on the boat, so I dug the genny out of the shed and had another go with it. Last week I put fresh petrol in it, but that doesn't mean the stuff in the carb float bowl is any good, so I bled the float bowl to get rid of the crappy fuel.
Then I gave a few tugs on the starter cord and it started second pull! It wheezed into life for a few seconds and then died. A couple more tugs on the starter and it started and stayed running, first with a huge cloud of blue smoke from the exhaust, which quickly cleared as it warmed up. After 10 mins on half choke I knocked the choke off and it still ran.
So a result there.
I dragged the sorry Seagull out and my concerns about the timing being out seemed to be confirmed. The locking screw on the stator plate is supposed to lock into a dimple on the crankshaft housing. But on unscrewing the non-standard screw fitted it doesn't seem to be long enough to lock the stator plate. As I turned the stator plate with a screwdriver down the screw hole trying to find the dimple, a quantity of old araldite came out from between the plate and the crank housing. It seems that's what was holding the plate in place.
So it's been bodged by previous owners then. I guess the fact I couldn't find the dimple is because its filled with araldite. So it may need the flywheel taking off and a clean and reassemble. Some Googling to do over the next few weeks then....
And buy a new locking screw.