I usto have a gator tail boat 18x 48 and it ran we'll I have a 3/16 18x46 and it don't really run like it should it runs flat the whole bottom of the boat makes contact. With water where as my gator tail boat would run with bout 5 ft in the water .We'll come to find out my transom is 19.5 on my new boat . Where as they should be 21 like on the gator tail boats. Gator tail boats have that double angled transom with that 45 at the bottom and my new boat is a old style with trim tabs should they both be 21 or will they be different with the different transom styles

Straight up with a right angle that's how I was told

Here's a reference for those that don't have a link. http://www.seamount-mattson.com/trandiag.htm

Mines also at 19.5, would it perform better at 21"? Would we see a performance gain in speed and holeshot? Thinking about getting mine welded to 21" just curious if i will see any gain by doing it.

I ran mine this weekend at 21 inches just blocked it up dint see that much of a diffrene at all may just split the diffrence and call it good

I know this is an old post but I just put a GTR in my prodigy, my transom is 19.5” and the dealer mounted the motor with a 1” gap between the transom and the motor mount. I don’t like they way they did it but it was done when I picked it up. They talked to Bubba at GT and he told them to mount it like that and to run it in the top pin. The motor vibrates like a mofo, not sure if it’s a prop (stock 2 blade) or because the motor is not sitting all the way on the transom. Did you end up keeping it at 21 or do you think 19.5 would work fine.

Good to know Bubba at gatortail (a salesman and not a performance or shop guy) is telling boat companies where to mount motors.....smh. It should be mounted flush to the transom and should be 21 inches. If your transom is not 21, adjust he Lin and run it each setting and see where your performance is at with each setting