I have a recently purchased 1986 Mercury 90hp inline 6. I dont know much about the service history but want to replace the water pump. I have never done this before but have the clymer manual. Is this a difficult job? The only thing that scares me from the manual is the quote "If the unit is equipped with a one-piece drive shaft bearing, the water pump base must be properly shimmed to maintain the correct forward gear backlash." They go on to say this shimming requires a depth micrometer, whatever the heck that is. I know I dont have one or know how to use one and certainly would have no idea what to use for shim material. This manual covers so many different models I am not sure if my '86 90hp merc I-6 falls into this shim catagory. Do any of you merc experts have any ideas about whether shimming the water pump base on this model? Thanks so much for your help.
