Mercury 250 pro xs problems

[harv1217]

Serial # 1B702192

Triton tr200
Mercury 250 pro xs
10” slidemaster 2.75” ptp

when running the motor for the first time of the day it will run its best pass of the day, anything after that the rpms will decrease. This morning the boat ran 5600 rpms with all new coils, give it two hours and it runs 5400rpms. The 5400 rpms only comes at 2/3 throttle, if you push hotfoot all the way the rpms will decrease to 4900. I have replaced all coils, new reeds, injectors, checked for turned sleeve, new spark plugs, gone through fuel system. At a loss on what to do now.

[lpugh]

Probable low fuel volume or slipping drive belt, Fuel/air pressure tests would be in order I think while problem is present or check everything in the fuel system and measure the torque required to move the tensioner about 75 in lbs minimum I think