Hi all I just replaced the impeller on a 20hp 1967 johnson after I put it back together I noticed in the book it calls for a washer to be placed on the top part of the driveshaft? should mention its a selco manual. I did'nt notice any washer when I had the LU apart should there be one there? also can the seal behind the prop be replaced without tearing the LU apart? Thanks for any and all info. Jim