This happened to me a few times over the years on my champ. I just kept moving it until I had screw holes all over. I pulled the carpet back and filled all the holes with marine Tex. Then I put a thick. Coat of marine Tex over the entire foot print and reinstalled. There is probably a better way but mine has held tight for the last couple years. Good luckJD
1996 Champion 191 Mariner 200 EFI original owner!
2013 Basscat Puma FTD 250 ProXs 10' Blades