Been on the River Dart this last week - engine has been running fine all summer until this week. After the first day's pootling on the river at 5 kts or so it started cutting out at idle/taken out of gear towards the end of the day. Got slightly worse for the next two days and was a real PITA when trying to manouver in the harbour as each time into neutral or if trying to go dead slow it died. Out to sea at other rev ranges or WOT it was fine and got full power.
Cleaned carb about 15 hours ago and it was spotless anyway, new plugs then too.
I checked plugs after issues above and they did not look too oily but cleaned them to no affect.
Pumping bulb when engine idling/dying has no affect - bulb is hard too.
Just had it in water bucket and the same again, will not happily idle below about 1400, drop it to less and then 1200 and it gradually gets rougher and rougher, more erratic, slows and dies.
Any ideas please chaps?