My first

[oldfielder]

If the starting circuit is bad it is not drawing-the problem could be any number of things. I know you checked the grounds in earlier posts,but did you take the main grounds off of the block, clean surface and put them back on. You should be able to find them-check the stud coming from the block and check the terminal on your ground wire. If the grounds are new (from re-wire), something may have gone wrong when he tightened everything back up-maybe a gound went bad after you ran the boat for a while. All of your new parts are certainly narrowing it down to wire or connection, and if the wireis new, I'm guessing connection. My mercrusier has two block gounds on the back of the block-they can definitely get sketchy if not checked once in a while.
This is turning into an old-fashioned barnraising.