1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 180Get this manual
11Remove water pump base Water Pump (Design 2)NOTE: Disassembly procedure for DESIGN model water pump is the same as for DESIGN model water pump, previousIMPORTANT: Gear housing on CYLINDER MODELS 70, 75, 80, 90 and CYLINDER MODELS 100 and 115 have been modified to accept new style plastic water pump base (PN 19282A1)This new base does not require gaskets as it has silicone impregnated seal on the top and bottomAs long as this silicone seal is not damaged i.e cuts or abrasions it will retain its sealing capabilitiesThis new water pump base CANNOT BE USED on older gear housingsThe aluminum water pump base (PN 43055A2) is still available for use with the older gear housings