I recently bought a used boat with a Force 120 (Mercury, 1997) motor. The drive shaft for the propeller does not have a cover over it...You can see the big nut on the shaft. Just wondering; Is there supposed to be a cover over this opening? I looked on-line for parts but couldn't find a cover or even an picture of the motor showing whether or not there is supposed to be a cover. If there is supposed to be a cover, please provide a link to where I can buy one.