help needed with a 1/2 V6 sst75

Hi everyone I,m after some ideas with a sst75 I,ve built as to why I,m having a problem with the engine clearing it self. the engine is a 2.4 merc block running a slide front and digital ecu, on a load wheel at the ramp I can rev the engine up fine with engine temps of at idle around 450 degrees, mid range rpm of 750 degrees and wide open 8500 rpm at 1100 degrees but then put on a prop and the boat in the water and it becomes sluggish in the mid range so off the dock and out of corners it is as if its fueling up and takes some time to clear itself witch is becoming annoying as once it clears the boat takes off. I was wondering if anyone has come across this, am I doing something wrong, because it only a 1/2 V6 do I need a different chip or even a custom chip with a different fuel curve or is it as simple as I,m over looking something through out the build that I should have put in or taken out that's causing this problem.
Thanks any input would be very appreciated. Thanks Joe.

i'd check water temp,

I started with a 2 liter chip in 48 merc box in my 1/2 2.5 u can drop fuel pressure some if it over prop it will load up too they seem to work better with a horn the vacum to regulator is pultsey with slide since only three cyl pulling . may be able to tie all three cly together on one vacum line to regulator may work . WITH BANK DID U USE if you use the 135 bank fuel could be building in lower bearing due to no push on fuel bleed line to push to top bear u will have to run the lower bearing fuel return to a vacum cyl to keep lower un used cly from pooling fuel. may be easier to call me if u would like 803-823-2121

thanks guys for the input every thing you say is much appreciated
thanks again Joe