I am looking for some advice. I have a Yamaha vmax sho 115 on my Bennington. Winterized the motor and added stabilizer to the fuel. Here in Ontario Canada it sat for nearly 8 months. 51 hours on the clock. It fired right up out of storage and burned off the fogging oil. First run was great for about 5 minutes. Suddenly it shuddered and wouldn't go over 3400 rpm. Back to the dock. Added octane boost, changed the fuel water separator and waited a day. Boat still idled rough, and could only get to 4600 rpm. Fuel consumption was deplorable. I then removed all but 5 gallons of fuel and added 13 gallons of fresh 91 octane with ring free. Still runs very rough at idle but smooths out at 4000 rpm but max rpm is 4800. Should reach 6000. Am I on the right track with fuel? Change plugs? Fuel filter?