I recently been doing alot of maintanance. I took the boat out and noticed a decent amount of water coming out the left sponson.only entry i can see for water is the plug so i pulled it and the rubber gasket on the back is shot.could i use silicone or goop? Or do i need to track down the gasket? Looks like this http://westmarine.com/drain-plugs/attwood--stainless-steel-garboard-drain-plug--9766445
I would go the gasket route, buy a new garboard if you can't find a gasket, just fix it right from the beginning.
You probably have the materials already... You can make a gasket out of a bike tube rubber and silicone (waterproof window silicone) it well.