Can you run 100% syntehic oil mixed 50:1 in the tank for a 1993 Johnson. I did this now motor want hardly run, sneezing alot when idling, give it the gas and it starts by taking the gas then just starts to die. Put new power pack on it in feb. Any thoughts ? I put 20 gals of fuel, star bright enzyme fuel treatment(2 oz), and about 8 oz of sea foam in thank? Did I do something wrong. Also put on new fuel filter on a month before this trip with new fuel line and buld boat been running fine, Ran fine for about 30 min.