I have a 2003 merc 200 salt water series outboard with about 200 hours on it. when I try to get on a plane the mortor will rev up to about 2000 rpm's then it starts missing. I have changed the fuel/water seperator and spark plugs. no change! when I pulled the plugs I found that the #3 cylinder plug was rusted on the out side but inside of the plug had vary little oil on it. it looked almost red on the center part of the plug. dose any one have an idea what could be wrong. thanks

See if the gas you are using has ethanol;

If so try cleaning out your carburator bowls and hight speed jets.

There is a product called Startron, a gas additive that is suposed to help keep the carbs clean. Ethanol is causing problems here because we just switched from using MTBE another fuel additive.

I found this out from a Mercury service department that has been dealing with this problem. Dry gas will not work because the ethanol/water mix floeats in the gas rather than sinks to the bottom of the tank. This gunk is supposed to clog the high speed jet which flows only when above a cetain RPM. So you may be able to idle but not get the gas when you need it.

I'm going to try it ASAP.