1985 Mercury Outboard V-300 V-3.4L Shop Service Manual, Page 107Get this manual
CLEANING and INSPECTION Cylinder Block and Crankcase Cover IMPORTANT: Crankcase cover and cylinder block are matched, line-bored aembly and never should be mismatched by using different crankcase cover or cylinder block
ACAUTION
If crankcase cover or cylinder block Is to submerged In very stron9 cleaning solution, It will be necessary to remove the crankcase cover cylinder block bleed system from crankcase cover cylinder block to prevent damage to hoseand check valve
ITh oroughly clean cylinder block and crankcase coverBe sure that all seala nt nd old gaskcu rc removed from matching surfacesBe sure that carbon deposits are removed fro exhaust ports2Inspect cyli nder block and crankcase cover fo cracks or