I now emptied the fuel line, cleaned the fuel filter
(again), and I emptied the carb from the drain screw. Pumped in some isopropyl alcohol, and let that empty again. Gave away the fuel to someone who can use it (i.e. smarter than I am), and cleaned out the fuel tank
Yes, there was some water
in it, and a little black smudge. That alone could have been the only cause, don't know why I didn't see it the first time, but I find it kind of hard to empty the fuel tank
completely. Next time I will use a simple pump to pump from the bottom of the tank (before it is empty), making a lowest point, to get water and other sediment out.
Btw that tank is a 3 USG tank, so I'm happy with the size - just need to burn it more often!
I went to the gas station and I found some STP fuel system and carb cleaner. Filled the fuel filter half way up with that, as well as added some to the fuel tank before refilling with new gas. Pumped a bit into a container to check, and that was all clean, no sediment at all.
I also want to get my hands on some STA-BIL additive, but here in Hong Kong
it seems the only option is to buy it online. Or the shops that sell it don't advertise online!
I just took it on a shorter trip, and it seemed OK now. Waves were too big for comfort, single
handed in that small dinghy
it was hard to run it at full speed continuously without getting a good beating!
For all your help, I hope some others can benefit, there were some really good feedback here (and some funny
posts as well