25HP Merc - Low Idle Starting Problem

[Cordovakid]

I have a 1981 25hp Merc manual start which will start typically after about 5 or 6 pulls with the enricher engaged. After that, runs like a champ. Will always start warm on one pull, but ONLY if I advance the throtte to a higher idle speed. Once started, I can lower the idle back down as low as it will go and troll for walleye all day long... If I try to re-start the engine at the lowest idle (where it previously was running just fine), it will stall out right away and won't start again unless I choke / pull / choke / pull until it turns over - acting like it's flooded.

Any thoughts on the reason for this problem? Spark issue possibly - however, I didn't think this was the case since it will idle down so well and purr like a kitten when trolling.