Mercruiser 3 inch Exhaust Elbow | Sierra 18-1971Mercruiser 3 inch Exhaust Elbow Sierra 18 1971 Replacement elbow for many early Mercruiser stern drive marine engines with log style exhaust manifolds. Sierra exhaust elbow For 3 in. ID hose 3 in. x 2 3 4 in. mounting pattern For Mercruiser 140 GM 181 CID engines from 1968 1982 For Mercruiser 165 GM 250 CID engines from 1970 1981 For Mercruiser 200 GM 292 CID engines from 1969 For Mercruiser 198, 228 GM 305 CID engines from 1977 1980 For Mercruiser