Attached is the quote for the new turbos and turbo gasket connection kit. Note that although these turbos are new, Volvo Penta puts a core charge of $610 on each of them. This core charge is refundable once I get your old turbos back here. Condition is not important as Volvo Penta just scraps these as of now. These are improved turbos.
But I am puzzled by your description of the fouling of everything down line of the turbo. Traditionally, if someone called with the description you gave, I would think that it was base pressure (tired rings that was allowing the oil sump to get pressurized and driving oil up and out) and that the oil was being sucked in by the turbo and being pushed through the system. But you say that the compression is good.
The second possible explanation is a leaking oil seal in the turbo allowing oil into the turbo which is then get blown into the rest of system. But it seems unlikely that both engines and both turbos would have the same type of leak at the same time. And turbo leaks are not that common and they usually get worse before finally the turbo seizes up.
The third possible explanation is that you have an exhaust leak somewhere that is spraying oil into the engine compartment which in turn is being sucked up by the turbos. You don't have another engine (like a generator) running or some sort of hydraulics that is spewing fluid into the air?
A couple of questions:
1) Is the turbo air filter all clogged up and dirty when you change it?
2) Is the crankcase filter all clogged up and dirty when you change it?
3) Are the engines running hot at all?
4) When you clean everything out, what does the stuff you are removing look like? Is it wet or dry? Is it black
or grayish or white?
5) Do both engines clog up the same and at about the same time?
6) Are you losing oil or anti-freeze?
7) What does the exhaust look like?
It could be the turbos, but not likely to have both at the same time.