Sportster "shaft protector" very important?

[Rogerswimuk]

Its #15 in the parts diagram linked below. It was broken off by a ski rope getting wrapped around it. Prop and shaft were fine, the plastic cover broke off. Just don't know if it had a seal or was just there for keep corrosion off the shaft. Looking to take it out this weekend and don't want to foul anything up. Any advice would help.

http://partsfinder.onlinemicrofiche.com/seadooforums/Seadoo_oem/Seadoo_JB.asp?Type=13&A=31&B=13