1967 80hp Johnson Sputtering at Full throttle

[wingyankees]

I have a 1967 80 horsepower Johnson Electramatic Seahorse outboard engine on a 1968 Larson All-American. We just recently got the boat and engine and it initially ran fine. The starter needed to be replaced and then it ran fine after that. We also replaced the voltage regulator and put in a new fuel line and purchased new gas tanks. The engine idles great and at low throttle it runs better than it did before we replaced the voltage regulator. Now our problem is that at full throttle the engine begins to sputter, like it's not getting fuel, but the tanks are full and the ball is hard. Once we bring it down to about half throttle it runs fine, but at full throttle it has trouble. Just wondering what else it could be and what we could look at adjusting or whatnot. Any help would be greatly appreciated.<br /><br />Tim