I have a 50 hp johnson oil injected with low hours, every so often for some reason it won't start unless I spray fuel down the carbs to keep it running . It smokes like hell as if it is burning oil from the carbs. after you run it out it seems fine again.It also does this on start up on occasion. Anybody know whats going on? my oil tank looks like there is a spout for a return line but nothing is hooked up.