I was told soapy water. I am about to do this, so it would be nice if a few chimed in. I am planning on using 3m weatherstrip glue in between the transom housing and the gasket, then silicone in between the gasket and hull since my hull isn't in perfect condition and needs a few low spot areas taken care of/filled in, then o ring on the bowl, (bowl gasket dry), then adhesive sealer on the surround of the transom to hull, and the transom housing to bowl area. Before, there was a S*&% ton of silicone in place of the o ring and the transom housing was only silicone and it was a mother to remove