If the motor lowers and bounces while making a noise or noises, lube the tilt tube pivot fittings and tighten the tilt tube nut on the stb. side 1 flat (1/6 turn) at a time until the bouncing stops.
If it goes down smoothly but makes a groaning or grinding sound, the upper mounting pin and bushings may be dry or corroded. In that case, sometimes a penetrating oil may give temporary relief but it is best to prop up the motor and remove the pin, clean and grease everything, and re-assemble.
"There is never just one thing wrong with a boat";
-- Travis McGee, main character in a book series by John D. McDonald
The factory recommends that a properly trained technician service your Johnson or Evinrude outboard motor. Should you elect to perform repairs yourself, use caution, common sense, and observe safety procedures in the vicinity of flammable liquids, around moving parts, near high-temperature components, and working with electrical or ignition systems.
The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.