I have a 1988 Tx 17 i just got on the back of the boat there are four holes one directly under the motor which is the drain with a plug there is a hole to the right of it which is the livewell intake then there is a hole in the upper right hand corner which is for the bilge pump the hole i dont know what it is is the hole in the bottom left corner that seems to be another drain but there is no plug i know this part will be under water and i was wondering what it was