I am considering buying a 1994 Johnson 115hp outboard. The shop has the engine torn down now, and the mechanic says he is going to bore all cylinders 40 over, replace pistons, bearings, water pump and rebuild the carbs. He says the reason for going 40 over, is that one cylinder had a 30 over piston in it. my question is, will 40 over leave the walls to thin, or is it ok to bore this much? The mechanic told me it could be bored up to 60 over. 