TOPIC: 1965 merc 500 won't start

I had the engine running fine, I revved up the engine to clean it out before shuting it down and it just died, like I turned the key off. It would not restart. I checked for spark and had none. A few minutes later I had spark but it would not start. The only way I can get it to fire at all now is to hold it wide open and squirt starting fluid in the carbs.It will fire a few times but will not stay running. The timing is lined up, good compression, clean carbs. Any help is appreciated.

pull off the magneto portion of the distributor and go through it. It could be a ground issue, a dirty or cracked magneto or your condenser took the big ride out to where the buffalo roam. Be sure the points look OK not unevenly worn or excessively worn.
Sounds like you have compression you have fuel but eratic spark. Go through the magneto. 7/16 wrench 4 machine bolts and off it comes. Be sure your plug wires are free some come off with it. Be carefull you do not crack the distributor cover.

One last thing check your fuel pump. Be sure it is clean the diaphragm is good (not excessively worn of has a hole in it) and the check valves are clean and working.