Mike.
Nothing to do with your symptoms, but - - I used to have an old Mercury 50 Blue Band.
It would start fine and run for a few hours. Then it would die and take hours of pulling ( yes Rob ) to get it going again.
The next day it would start fine again.
After cleaning the carbs and changing plugs etc. it was just the same.
I thought it was coils but never found out.
Bloody Mercurys ! !
Jim