I don't know which manuals you have, Fred, but here is the large one-piece flo-jet:

[Linked Image]

We have had several cases here recently where these carburetors had developed slow flooding, due to wear on the float bowl seat. If you had left the fuel on when you couldn't restart, but had turned it off in the cases where you could cold-start easily, I'd just about bet that this is the problem. If you can report back when you have made the test, I can explain a couple of alternative cures, but if you have the manual you probably already know at least one of them.