98 Mariner 75 hp gas in oil reservoir

[Tbeaze2424]

Started running rough, cut off a few times, then wouldn't restart. It's my sons boat, I'm coming in on tail end. Found a few bad parts but kept smelling gas, I had disconnected the hose because it seems like the tank building up pressure would push some gas into carbs just sitting there. After still smelling gas, I opened oil reservoir cap and it was pretty much filled with fuel and very little oil in it. I've seen people talk about a check valve but from what I can find, there's no in line check valve on this engine, just a valve on top of reservoir. Any help would be appreciated.