Hey ive got a neptune with a 52 on it....The plane uses up about 80ft of water to take off, but then seems to fly ok (climbs a bit with power)
Im not sure if the motor is too tired or if ive got a thrust line/cg problem.
Any opinions to my excess runway prob ????

80 feet doesn't sound too bad.

Climbing under power could be thrustline or nose-heavy. How much forward stick does it take to fly inverted?
The 30-degree dive test does not work that well for seaplanes since a high-mounted windmilling prop causes a lot of drag up high, and pulls the nose up.