1978 Johnson 175, 200, 235 HP Outboard Service Manual, Page 72Get this manual
Figure 5-11Starboard Cylinder Head Removed
On the 235 hp model the powerhead must be removed from the exhaust housingSee page 5-7eRemove 28 screws and outer and inner exhaust coversSee Figure 5-12, view AfInspect cylinder walls, pistons and piston ringsPiston rings must be free in their ring groovesCheck for scuffing, scoring and damage caused by overheating, lack of lubrication or broken piston ringsUse an inside micrometer and measure cylinder walls for wearIf worn in excess of 0.004" (0.10 mm) over specified diameter in Section 2, cylinder should be rebored to next oversize and fitted with an oversize piston and ring assemblyIf damaged, power head will have to be removed and disassembledgIf cylinder walls and pistons are in good condition, clean cylinder, cylinder head, exhaust cover and gasket surfaces to remove old sealer and gasket materialSurface cylinder head and exhaust covers as described in "Cleaning, Inspection and Repair, Gasket Surfaces" on page 5-7 hApply OMC Gasket Sealing Compound to gasket surfacesDo not use sealer if so stated on gasketReinstall cylinder heads and exhaust covers using new gasketsTorque screws to specifications in Section 21Inner exhaust cover 2Gasket 3Outer exhaust cover