I have a 1997 Tracker outboard 25HP two stroke. Its made by mercury marine. The impeller has never been changed. I know the lower unit has to come apart to access the impeller. What i dont know is if there is anything else i need to know, do i need to put it in nutreul or does it need to be in gear? Is it ok if the prop turns after i remove the lower unit? I just dont know if theres something else i need to know. This will be my first time changing a impeller. Thanks