I decided to change my Alpha One Gen II impeller, so I obtained Mercury part # 817275K05. This kit is for drives s/n OD469859 and up - which my s/n OM xxxxxx falls within. For a "first timer", things went well until I installed the face (slinger) seal. The seal included had a bottom flared lip that was bigger in diameter than the installation tool included. Given that this was my first attempt, I did some reading and you tube watching and was familiar with how to install this seal. Plus, the kit came with pics and instructions as well. At this point, I have no idea if my seal is properly installed or not. The instructions say while pulling the shaft upwards, push the tool down until it makes contact with the pump housing. This will put the seal at the right height.This is actually impossible since the bottom edge of the face seal is larger in diameter than the bottom edge of the tool itself. In other words, the seal will not fit inside the tool itself.The tool will never touch the pump housing. It can only rest on the flared edge of the seal - which makes contact with the top of the pump housing. Normally, I wouldn't be so concerned, but there is a stern warning on the instructions about improper installation resulting in stern drive damage. When I checked my old seal, it fit inside the installation tool like the instructions showed, but my new one does not. Either I have the wrong seal in the kit, or Mercury changed the size of the seal and didn't bother to change the size of the tool or re-write the setting instructions. Please excuse the lengthy post, I just wanted to pass this information along. One additional item, the instructions said to put a light coat of grease where the seal lip contacts the pump housing and to ensure no grease was on the shaft itself. This meant that the seal didn't exactly slide down the shaft very easy.