Fuel in oil of a yamaha f15eshd

[BeaverAggie]

Howdy,

Briefly, my parents are cruising in Central America and has recently encountered a recurring problem of fuel ending up in oil. My mom is currently visiting her mom in the states, so if anyone can suggest some parts that might help fix the problem she can take them back with here. Here is what he describes as the problem: (sorry for the length!)
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The main problem is fuel is getting into the oil fairly large amounts in a very short time. I ran it for only about 10 minutes and then sat for 4 hrs with the hose hooked up and there is about 3 or 4 oz of fuel in the oil. I had just drain all the oil and changed the filter I know there was nothing left to contaminate the new fuel. It runs perfect as long as you don't hook up the crank case blow by hose. The float is not sticking, even though it might have been in the past when this started, but I am almost positive it is not sticking now. it is not floading like it used to and not run even when the hose wasn't on. Before it has lasted a couple of days before it had fuel in the oil, today it was ten minutes. there has got to be another way fuel can get into the oil besides a stuck float. One day the cylinders were so full of fuel it wouldn't turn over, but that was when the float was sticking. There was also one day when there was some salt water in the lower cylinder not much but it was there. The hard part is going to be able to explain this to some non english speaking person if I can't figure it out. It has also never heated up so I don't know how I could have cracked or blown something. the damn this isn't even 4 yrs old. It does get a lot of use though. When it was stored last summer for two months I drained the fuel. It has run fine till a month ago. It started after buying fuel in El Salvador. I still have the same fuel but why would that cause fuel in the oil if nothing is currently sticking.

[Silvertip]

Although the float may not be sticking, the inlet needle and seat may not be sealing tightly when the float rises. This condition allows fuel to continue to flow into the engine. When you refueled you may have picked up some debris that is lodged in the inlet needle and seat. Float level that is set too high can also cause the fuel to continue to run into the engine flooding it. Lastly, if the fuel tank is located above the level of the carb and any of the problems mentioned exist, lack of an anti siphon valve on the fuel tank can flood the engine. The obvious fix is to correct the carb issue. But the tank should have an anti siphon valve installed if the tank is higher than the engine. This device prevents fuel flow to the engine when it is shut off. they look like the one below.

[BeaverAggie]

Silvertip.
Thank you for the helpful hints to check out, I will pass them on. I know the fuel tank is in the bottom of the dingy well below the carburetor. I also know flooding has been an issue, but he is just curious why all the sudden fuel contaminates the oil so much quicker these last couple of times of use.