filling small holes in hull

[colad]

Hi,
I just purchased a new fishfinder to replace my old one and the transom mount is different so I will need to drill new holes. This will leave three holes from the old mount. Is there a recommended way to fill them and make them water tight or is it basically lust fill them with marine grade sealer and I am good to go? any advice is welcome, since they are below the waterline I would prefer not to sink my boat :)
Thanks!

[allingeneral.com]

You could probably get away with using sealer in a pinch, but if you want a permanent repair that looks good and lasts for a long time, check out the instructions at these links:

http://entertainment.howstuffworks.c...in-a-boat1.htm

http://www.blumhorst.com/potterpages/gelcoat.htm