Mate, you seem to know what you are doing ref engines and two strokes. Imagine your lump was a two stroke motorcrosser. It might 'tickover' ok then fuss about a bit whilst getting to revs it likes, as they do. If She idles ok and gets up on 'main jet' ok dunna worry. Two strokes as you know don't like it when not underload. I would leave well alone for now and run Her for a few hours. 1994 eng, is quite basic technology. As a rule of thumb though, if you have low speed/revs prob, it is a problem with the 'low tension' side of the ignition system, ie the stator or coils therein. Plus anyway, what are you doing at 4-10 kts? Pedal to the metal Mate!!