You have to wonder what the Mercury engineers were thinking when they designed that cowling with the recoil starter built-in. Remove the cowling and you have no starter. Sheesh.
With a small engine like your 4HP….a simple adapter like is mentioned by Crosbyman will work fine. Or you can find a suitable rope pull from some old engine and adapt it. The picture I have shows one from an old Scott Atwater 3.6HP but there are many others that will work .
Or….you can buy a custom starter with a built-in over-running clutch. There are adapters available for your electyric drill that would provide the added safety of the clutch. A bigger concern with larger engines though. Not so much for your 4HP.
https://www.bbtstarters.com/aboutus1
