I have a 1999 Johnson 50hp 2stroke on a 16 foot c/c. Was on the lagoon sunday and she ran great for the first hour. Started making a run with the engine wot. The engine started making a noise, as if grass were on the prop and I lost power. Powered down, trim up and no grass. WOT again then a few moments later same thing, power loss and a strange noise from the motor. One more of these and she gave out. Would not start again. My partner thought it was getting starved for fuel. 3/4 of a tank. bypassed the fuel/water seperator and still would not start. trimmed up to look at the plugs and the lower plug had a significant amount of corrosion on it. Around the metal part the socket holds onto. Pulled the boot and it looked ok but still would not start. My friend, who is more mechanically inclined than I am, thinks it wasnt getting a good spark because of the corrosion. I have not had a chance yet to test the theory. Any other ideas? no alarms from the motor and regularly maintained by a good marine mechanic. When trying to restart it would start to go...made some gruting but would just die out.