Mike wrote:

1) no (or very little) oil usage.
Check for fuel dilution.

3) Turbo output 2600rpm (port)16psi (starb) 18psi Cummins manual
calls for 20-25psi.
Worn turbos are less efficient. Worn bearings will limit turbine speed
and reduce output pressure. How much power or boat performance have you
lost? Turbo output pressure is related to the load on the engine, and
atmospheric pressure and temperature, not just rpm. There are a number
of reasons why the pressure might be low ... what was it before you
decided you had problems? Do you know what it was?

The smoke and sheen that I see are unburned diesel.
Are you positive it is fuel? Do the engines smoke black on acceleration
and under heavy loads? What color is the smoke at low speeds? How much
power have you lost?

turbo pressure not getting enough air into the cylinders. The low
turbo pressure is Caused by bad oil seals in the turbos allowing crankcase pressure to
be reduced by the vacuum of the turbo compressor.

????? Crankcase pressure related to turbo vacuum? Sorry but you have a
diesel, there is no "vacuum" created anywhere. There is a low pressure
area in front of the compressor wheel but unless your air inlet is
blocked there is no vacuum like you might see in a gasoline engine.

The only effect you would see if you have bad oil seals in the turbo
would be oil leaking into the charge air and being delivered to the
cylinders or blue oil smoke in the exhaust. Check the condition of the
intake piping to see if it is wet with oil, check the condition of the
exhaust from the turbo after a period of idling to see if it is wet with
oil. It sounds like that is irrelevant now that you have removed the
turbos for rebuild but file that away for the future.

Worn injectors will cause poor combustion and can create most of the
symptoms you describe.

As long as you have no starting problems you have no compression
problems. You may have cylinder wear and worn injectors which lead to
fuel dilution of the lube oil. This is cause for concern. Check with
Cummimns for their recommendation on maximum allowable dilution limits.

Good luck and get back to us with the results of your investigations.