You have to be kidding - right?
Faster is right - a 50 hp outboard would be ridiculous.
First off - it won't fit in the engine cutout in the transom, if you got it to fit somehow, the entire G-26 transom would break apart when the engine went into gear. The weight would have the stern way below the water line. A larger engine will not make the boat move any faster - it won't plane no matter what you put on it.
The maximum engine size for a G-26 would be under 10hp. A 9.8 four stroke with a 4 blade prop moves the boat comfortably at hull speed running at about half throttle.