Chris nailed it for the most part.
Here is clams procedure for those reading at home; http://forums.iboats.com/showthread.php?t=168855
The tang screw is the screw that adjusts the stop when the carb butterflies start to open when the throttle cable is operated.
Basically when the pickup just contacts and starts to open the butterflies you should be reading around 3-4 BTDC while static timing.
Dont worry about grounding all the plugs as long as one is, if your cranking with the starter I would just disconnect them all but #1 that will have your timing light connected to it anyways...
Hope that helps!
Cheers,
Jon
