I have a 1990, 90 Hp VJ90TLESB engine. I can remove the drain plug, but the fill plug is stuck pretty good. The plug has a single slot that looks like a flathead screwdriver could work, but the slot is sort of wide and not too deep. It is very difficult to get any leverage on it before the screwdriver tip slips right out. I've tried a hand screwdriver, a hammer drill, and PB blaster. Can anyone help?