Just screw them out with a T40 bit.
It is a insert on the inside of the hull, you dont need to remove the top deck. But if you are removing the sponsons, make sure you put the screws back in. The inserts will pop out of its little "spot" when u jump waves and water will also enter the hull with the screws out. Dont worry about sealing the holes, i didnt use sealant when i installed the riva sponsons, and that seems to be pretty dry. I think the torque spec is 11NM
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