I am trying to remove gearcase head assembly 0383757 oil seal on a Johnson 1974 25hp motor. I thought seal was similar to other seals and proceeded to remove it by tapping around the back perimeter edge of seal with a drift pin. This method had no effect on seal other than to fold the metal casing down and deform the top face of seal. The casing is a much heavier metal gauge than other oil seals and it seems that casing is an integral part of assembly as it has not budged a fraction after a week of effort. I have looked on the net but can find no info, or examples of any other seal other than the ones listed by various part suppliers seal # #0321787. Does anyone have any ideas how I can remove this seal without damaging the assembly. Any help would be appreciated. Thank you.