When replacing impeller ,I always have trouble getting reverse gear. Is there a trick to this? I have tried several ways before . I am now working on an old 1966 110hp 1100ss Mercury. I purchased a used lower unit last year, installed without a new impeller but had no reverse . Pump quit this year . I put shift lever in forward then dropped lower unit. Ggoing for new impeller tommorrow. Are there any tricks to putting lower unit back up and getting forward & reverse gears?