1989 Mercury 25hp shuddering/knocking at high speed

[EarlyCuyler]

I have rebuilt this 25hp Mercury. New carb seals, insides, everything. It’s starts and runs great but when put under a load, it’s hesitates at full throttle, 3/4 throttle runs great. Is my boat too heavy or what ? 15ft flat bottom, built front deck 2 batteries, trolling motor, electronics, 3/4” wood flooring. Pretty heavy loaded down. I’ve changed the coils and everything,

 

[Texasmark]

Might move the LU out, PTT or pick up the next notch in your tilt bracket. Come back. A tach would help immensely.