older 50 merc with fuel/oil leak

I have an older 50 merc (late 60’s?) that is leaking fuel/oil from the powerhead. You can see the leak bubbling at the crankshaft cover gasket. The motor starts and runs OK, however after you have warmed up the engine, if you turn it off, it starts up again OK, but will stall every time you try to put it in gear. If you don’t turn it off, she’ll run all day, no problem. When it stalls, the only way to get it going again is to put the high idle to Max for a couple seconds, let it ‘scream’, then put the idle back down to normal, and she’ll run no problem. I don’t know if the engine is flooding? Either way, I want to fix up the leak (as it drips into the lake), and am wondering if these two problems are related? Any suggestions would be appreciated!