Leak is normal...carbs sound like one is lean. Check under cowl for dirt dabber nest in air intakes
Funny thing about this outboard is if it sits up more than a week it seems to run like crap. I have to pull all 4 carbs off, clean them and then reinstall them. I do not know why. I use ethanol free gas now with Lucas Marin fuel treatment. I have tried sta-bil.
Nothing will get me past two weeks of it sitting. I have all new lines, fuel filter, new primer bulb and tank. I tried a fuel water separater and I could not get the boat to run correctly. I’m guessing the 1998 mercury Bigfoot 50elpt4s is just a bad design. I’ll attach a pic of the carb setup. It’s just like the same year Yamaha.