Question about Mercury Oil Injection System

Hi, i just purchased a sun tracker pontoon with a 2003 50 hp tracker mercury engine. I like the oil injection system and i really dont wanna remove it and mix the gas myself but it has a problem, It seems to work good but im getting leakage somewhere. If it sits for a few days or a week in between uses i notice my oil level in take will be down some and usually there is some oil sitting in the bottom of the motor area, when i start it it will blow a bunch of oil out the exhaust. Unless i use it every day or two its really not noticed but if it sits a few days it gets pretty bad. My question, is there some kind of check valve or something that could be bad letting it to siphon oil thru into the cylinders while it sits? I removed the oil tank and there is no oil leaking from the tank or hose that goes over to the pump so it has to be coming from somewhere else, wherever its coming from is allowing oil to leak into the open area around the engine block itself and also allowing it into the internal part of the engine causing it to blow out the exhaust when first fired. If i cant figure it out i was gonna do away with the oil injection system but after reading how reliable they are it just seems so much easier. Thanks for any info guys, Sam