OK, had another session this afternoon - no change.
Checked all electrics - I really cannot stress how mint and well maintained this engine appears, seriously looks like it was assembled yesterday, electrics connector/bullets/terminals are completely like new, clean and tight.
Plugs less than 10 hrs old, clean and gapped perfectly.
Spark on each on is good and strong.
Kill switch works perfectly as intended.
Looks like I'll have the take the carb off..
I wish one of you outboard guru's lived locally!
I ****ing *hate* the things....