We recently purchase a 1996 Crest Savannah Gold 30 ft pontoon boat, diameter 26". We are planning to add a 16ft cabin. The mercruiser was a goner and we have just finished removing it. We have purchase a 2002 115hp Johnson to replace it. We understand that we must close the open hole where the foot was located. We are using alumium plate and will be using a jack plate. Looks like we will need a 12". We will be fishing in shallow water. Has anyone had to do this and if so, what problems will we be facing. We don't care about speed just installing an outboard to replace the inboard. Could really use help. Thanks in advance.