8 hp Merc Mariner Motor Issue

[cnoffsin]

I just got my first boat (16ft tri hull ski boat) and i bought a used 8hp Mercury Mariner long shaft 2 cycle motor.

The first two times i took the boat out it ran like a champ and i was thrilled. The next couple times i have been out it stalls out and will not run half as fast.

The guy i bought the motor from was real knowledgable and he had replaced the carbuerator spark plugs etc. the **** thing looks like you could eat off it on the inside.

i sprayed carb cleaner in it and that helped for a little bit but not long. it is spraying water out the back so its pumping water fine.

i thought maybe i put too much 2 cycle oil in the tank at first so i tried to thin it a little with another gallon of gas and that did not help.

any suggestions? thanks