I recently bought this motor and have it on a 13 foot narrow jon boat. Last trip out the motor would bog down severely and it was consuming a lot of gas. Changed plugs and found a rubber tube that goes from the bottom of the block to the top of the block cracked. I taped over the holes and sealed them because I cant figure out how to remove it without destroying it. Put motor in trash can full of water and it revs and runs a lot smoother. Wondering what that hose is and how to replace it. Also it has a lean/rich knob on the front. what is the proper way to set this adjustment? Thanks.