I have a mercury 110 that needs a little help. The pull cord has to have some help goung back in, and I believe that it could use a new carburetor.
You could try a couple of things. Pull the cover that holds pull rope. Inspect the parts that I gage the fly wheel, take some spray lube like graphite and lubricate around where the part that holds rope rotates. Could be dirty or check for being worn out. I think it rotates on a bushing in the center that could be letting it cock and bind. Also spring could have just gotten weaker over time. You could try winding the spring a couple of rounds tighter if everything else is good or may have to replace spring. On the carb I would run a couple ov good doses of sea foam through it first befor condemning it.