Ok, I will go way out on a limb and make some assumptions.
This boat has been yours for over two years and was running fine and this problem just started a year ago.
You did NOT buy this this boat with this problem.
If either of these statements are NOT true I would look at
"regarding return line
this engine has the return line
going back to 2nd filter back in the system from there, not the tank, dont think that would be source."
This set up bothers me because usually the return line has little or no pressure because it dumps into the fuel tank.
The current setup requires that the return line work aginst the head pressure of the lift pump (5-8 psi) and may cause a seal that works under zero pressure to leak when installed but not on the bench. A pluged filter on this line could also raise the pressure.
Personally I would route the return back to the tank.
If however the above statements are TRUE then you must bypass the lift pump (hose around) with a electric and eliminate the lift pump from system and test.
No increase in oil then you have found the problem--the lift pump.
Still getting oil increase then it is the injector pump since I cannot see the injectors running that much fuel by the rings and the motor running without looking like a stink potter.
Let us know how it works out.