▁B ▁ 2 2 0 ▁models . ▁Later , ▁the ▁larger ▁ 3 . 5 - lit re ▁M 3 0 ▁with ▁electronic ▁ign ition ▁became ▁the ▁B ▁ 6 3 5 . ▁Model ▁numbers ▁related ▁to ▁the ▁engine ' s ▁horse power . ▁ ▁Stern ▁drives ▁B MW ▁Marine , ▁in ▁conj unction ▁with ▁Z F , ▁designed ▁and ▁manufact ured ▁a ▁new ▁stern ▁drive ▁unit . ▁These ▁stern ▁drives ▁were ▁market ed ▁as ▁the ▁B MW ▁Z - D rive . ▁Un iqu ely , ▁these ▁stern ▁drives ▁util ized ▁a ▁multiple ▁wet ▁cl utch ▁system . ▁These ▁drives ▁competed ▁with ▁Sweden ' s ▁Vol vo ▁P enta ▁and ▁Mercur y ▁Marine ' s ▁Mer c ru iser ▁Division ▁of ▁Still water , ▁Oklahoma . ▁ ▁Dies el ▁engines ▁To ▁further ▁comp ete ▁with ▁Vol vo ▁P enta , ▁B MW ▁added ▁small ▁dies el ▁auxili ary ▁sail ▁boat ▁engines , ▁r anging ▁from ▁ 7 ▁to ▁ 5 0 ▁horse power , ▁to ▁the ▁B MW ▁Marine ▁product ▁line up . ▁The ▁engines ▁were ▁based ▁on ▁four ▁air - co o led ▁dies el ▁engines ▁manufact ured ▁by ▁H atz , ▁then ▁mar in ized ▁by ▁B MW ▁Marine . ▁Hur th ▁Marine ▁transm issions ▁and ▁instrument ▁pan els ▁were ▁added , ▁and ▁the ▁resulting ▁marine ▁systems ▁were ▁market ed ▁as ▁the ▁D ▁ 7 , ▁D ▁ 1 2 , ▁D ▁ 3 5 , ▁and ▁D ▁ 5 0 ▁engines . ▁The ▁engines ▁were ▁among ▁the ▁first ▁in