Hello all, I have a 1984 Evinrude 15hp 2 stroke. Overall it works great, had some work done on it last year and had compression checked etc... and all is good. This weekend i took it out for the first trip of spring and it ran great except the last hour. When i ran it full throttle it ran half as fast and when i ran it half throttle it ran full speed. It ran perfect in neutral though. I used gas that was stabilized last November mixed with new gas/oil. I'm thinking it could be something as simple as bad gas, bad spark plugs( changed them last year though) or maybe a weak diaphram in the carbuerator. Anyone ever have this problem or work on motors and can lend some advice it would be appreciated.