Diesel Doctor

[nealer2]

Yesterday I was coming back from Catalina Island to Long Beach cruising at 1850 rpms (14.5 knotts).
When I reached the breakwater, I pushed the throttles full, the engines reved up to 2035 rpms and then the engines seamed to rev-up but the boat slowed, almost as if the props were cavitating or caught air pockets.
I backed off rpms to 1400 and the props seamed to dig into the water and push boat back to speed.
I again push throttles all the way forward and again the boat slowed and engines reved.
Is there someting wrong with the transmissions?
I checked the oil while comming to slip and under forward power. Starboard was at full mark, port was way over full mark! Also the port engine oil at was at 3/4 full. My partner indicated he filled the port engine a little over full before our trip.
Could there possible be a seal between engine and trans that has gone bad and engine oil is leaking back into transmission, thus being over the full mark?
Would the transmission slip if oil is over the full mark when rpms are increased?
By filling the engine oil over full mark would this create more pressure to seal between transmission and engine?
I have Detroit 8v71 turbo (435 hp) with M20 allison transmissions.