While removing the lower unit from my 1999 suzuki DT 200 I pulled out the drive shaft and saw in the drive casing a rubber sleeve attached to a metal bushing that is part of the drive shaft casing. The rubber has dissentegrated and appears to be press fitted into the metal bushing. The drive shaft passes right through this. The microfiche does not identify this as a part - what am I looking at and is it replaceable?