Sorry I have just seen your post.
You probably want to look at this previous post
However, the symptoms described, might well also mean that your engine has at least one cylinder flooded with water. So you need to also check the riser installation, and or siphon break system.
Water cannot be compressed as air. So the Click when pressing the start button could mean that the batteries are not strong enough to move the engine while a piston is compressing water. Then you connect 2nd. battery , provide more power and get to start. DUring the week, something happens. You might try closing the engine water intake.
Hope this is not your problem. Quite expensive.