I think around 8-9 gallons per engine. But cannot remember for certain, any DD dealer should be able to tell you.
Approx 6 gallons. Depends how much old oil is left behind and where your filters are located and what size(s) they are.
According to the DDC book, total capacity on a 8V-92 TA 735 BHP marine engine is 27.5 quarts with filter. At a zero-degree installation angle, less filter, High is 25.4 qts. and Low is 18.5 qts. Max installation angle is 15 deg. Oil flow is 39 gal. per min. Did I win the toaster?
speaking of oil and DDs, many yards still use Delo 400 in those which has been reformualted aroudn 2003 and is no longer "approved" for use in 53, 71 and 92 series detroits. if using chevron, you need Delo 100 (straight 40), not 400! 7 years after Chevron/DD issued a service bulletin on this issue, i still see it happening!