Normally when using the flusher port on the back of the motor, you turn the garden hose faucet only about 1/2 to 3/4 open.
The specification is 20-40 psi of water pressure.
Make sure your dislodged water outlet tube is correctly and securely fastened in place before running your engine again. It is recommended that your dealer perform and inspect the hose and fitting and remove and install the engine's lower motor covers for access.
"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.