Dextron ATF is better. In the old days Ford had it's own special formula (Type F), which was not recommended by Mercury Marine. Not sure now.
Does the PTT motor run in the up position? If so, help it up by hand and lock it up. Now fill it with ATF, and let it bubble out air a bit. Now refill and run her down and up and let het sit a few minutes. Refill and run her down and up and let her sit. Now refill and repeat...... If that doesn't fix it, you have some sort of seal or check valve issue.
