ORIGINAL: steve111
I don't have an Oliver, but I'd be very suprised if one could manage 13500-15000 with an 8x6. I think you'd be doing well to get much more than about 12000 out of a good 2.5 diesel with that size prop. Perhaps those figures were for an 8x4 or 8x5?
10300 sounds pretty reasonable for your Drabant.
My well run in MOD Oliver Tiger mk3 turns a RAM 8x6 at exactly 12K rpm.
An APC 8x5 suits it much better in a Peacemaker.
Ray