Saving Old Seagulls

My 102 ran without any problems on and off for several hours, did the usual flush at home with fresh water/no prop and stored for a few months.
Next outing I started it on the transom on land for a minute, used the choke and varied the revs. No problem.
Launched it and it took off like a scalded cat, throttle control was useless! Ran for a minute or so. Then it stopped. I'd forgot to open the breather valve!
Rowed back to shore and had to use pliers too loosen it.
At this stage FB (forward ballast) was not pleased.
Started again (one pull) but all it would do is just above idle, no throttle control! choke open or closed. stopped and started several times but still would not get above idle. FB at this stage was about to mutiny.
Luckily I always carry a spare - the trusty 40+, used that for the next 2 days and 4 tanks of fuel! FB calmed down and enjoyed the boating.
Back at home, I removed the prop and ran the 102 in the tank without any problems!!!!
Dirt in fuel? Blocked jets?

Have a look at the throttle slide - is it moving?

Yes, I could hear it click shut and when I removed the shroud and could see it move up and down.

Then I suspect you are quite right. The fuel system is well worth a look, from the filter in that fuel cock, through the pipe, throught the banjo filter, and the jets.

Let us know how you get on. Mucky fuel can be a pain.