battery is fully charged, starter engages flywheel but it takes 15 seconds for it to turn one revolution, and wont start.its been sitting for a year.will outside temp make it slow?
Only if it was so hot that the flywheel melted into the engine. I dont think you would be keen to go boating if it was that temperature outside.
Pull your plugs out and see if it makes any difference. It should be pretty easy by hand then too. If its not easy you have an engine problem.
I suspect you have a worn starter, solenoid, or cables.
Check its not the engine binding up first