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Lower Unit drain plug stripped screw heads


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I have a Mercury 6HP 4stroke kicker motor that have stripped lower unit gear oil flat head drain screws. The top drain screw is the problem one because it is recessed, otherwise I could use a pair of vise grips to get it out. Any tool suggestions to get these drain plugs out. I used a grinder on a large screw diver but it is too large to fit in the slot now.

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Lay the motor flat, preferably on a set of sawhorses take a center punch put a good point on it then on the outer edge of the screw preferably in the slot angle the punch so that your in the off position left to loose right to tight, with a hammer tap the punch until screw loosens, might have go a little more than a tap and it will loosen. Make sure your on the most outer edge of the screw but not in the aluminum of the housing. I use like a 16-20 oz. hammer and like a little more than a 45* angle of the punch. Take your time and it will come out. There's no need for these plugs to be that tight. Good luck you'll get it.

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I have a Mercury 6HP 4stroke kicker motor that have stripped lower unit gear oil flat head drain screws. The top drain screw is the problem one because it is recessed, otherwise I could use a pair of vise grips to get it out. Any tool suggestions to get these drain plugs out. I used a grinder on a large screw diver but it is too large to fit in the slot now.

If you still have enought slot left in the screw file your screwdriver down to fit the slot, use a cresent wrench or vicegrips as low or close to the screw as you can and break the screw lose, keep steady pressure on screwdriver so it doesn't slip. hope this helps, it works for me.

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PAP has it that should work fine

Thanks guys, yes a small round punch would work, but with the center punch you can get closer to the outside edge and once the punch locates itself it's easier to to stay in the same spot. The jarring of the punch at the same time applying pressure to the screw in the out direction. I have removed many a screws and even bolts. I really think the jarring of the screw is what loosens the screw. Again good luck.

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Paps way works well,but there is another way which will also help you put the screws in without damaging the slot.

Get an impact screw driver and a torch. Leave the kicker on the boat.

Heat the screws up but not a whole lot. Take the impact driver,set it on counter clockwise and pick a bit that is as big as the slot. Set it in the slot and give the impact driver a whack with a hammer.

For tightening the screw set the impact driver on clockwise.

Just do not try to do these things with a screw driver that is not wide and thick enough because that's how you screw them up.

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