Semper FI fellow Devildog, it sounds like a few issues, the fact that ya got her to fire is good, I have learned to always go back to what you have changed,,,,, carb is a starting point, surging, I would look for a vacuum leak, recheck your carb, base gasket, any plugs you might have missed.. (did that one once) if you get it running, use ether, WD, carb cleaner, something around the spots where air can get in. Once you get that clear, check your timing, wiggle your rotor, make sure you don't have a lot of play, run your fingers down all the wires WHILE running, you will find out if you have a bad wire very quickly (again, had this one once, brand new wires) but with the surging, I would start with a vacuum leak search first.
Welcome home and Thanks for serving Marine!
Joe

 

two things i would check:

First is the distributor in exactly the right place? I have had the distributor out of both my 410 and 360 for detailing before being put back in. Since the engines were running fine before, idle mixture at 2 1/2 turns and idle speed untouched, I had no issues there. Neither engine would start but they would crank all day. So I went around and turned the distributor back a little counter-clockwise to retard in case too advanced. Almost started so a little move counter-clockwise and bingo. No matter how many times I have taken out distributors this is the one thing that can always catch me but I know the way to solve.

Second, is how much play is in your distributor since you are using points. A new distributor, that used bronze bushings, would have just .00025" of play. An increase of .001" of play would change your gap by .002". This would translate into your dwell ranging between say .014"-.018" when set for .016" as the rubbing block goes bouncing around the lobes. This would then vary your timing by 16 degrees as .001" almost equals 4 degrees and so the engine would run poorly. This is on a V8 engine as I know a 6 would be a little worse since there are 6 lobes dividing 360 degrees of rotation. To check this you hold the housing with one hand and the heel of your other hand on the opposite edge while you use the fingers to move the rotor side to side. If any play detected then your bushings are worn. Should note that more often than not when people think they have a carb problem they actually have a ignition problem. Heard one mechanic say that is true at least 85% of the time.