The lower level of a Johnson outboard houses the water pump and propeller, among other important parts. Two seals keep the water out of the gears and keeps packed grease in, so if the seals become damaged in any way this can cause lots of problems. Therefore, when a seal is damaged it must be replaced.
Start by removing the cotter pin and then the propeller nut. Place the steering wheel puller over the propeller shaft, then lock the arms of the steering wheel puller and depress the bearing carrier off the gear case. Remove the damaged seal and pull out the old O-ring. Place the new seal into the bearing carrier and tap it into place with a mallet. Finally, spread grease on the seal. Don’t forget to replace the motor oil with Evinrude XD 50 oil!