Thanks for the replies --- I have had the engine for 5 years (came with the boat) and just pull out the choke,give it 2 or 3 pulls and she is away then bang in the choke.
Because this summer has been so cool,the boat been idle for weeks on end as opposed to days and also no heat from the sun on the engine cowl to add some warmth my usual starting method seems not to work.
Now that I know what the choke knob actually does then I'll try different cold start methods --- the word "start" on the knob should have been a clue !!
I had an audience of 1 on Monday --- a guy sat on his Orkney waiting for the tide .
My engine eventually started and I went fishing ----- on returning Mr Orkney was still high and dry ---- I love these neap tides !!
Thanks again for your time and hints --- I have found out a lot about my motor since posting here . I await the next time I try to start it.