A marine propulsion device information transmitting and receiving system comprising: a server ; and a watercraft including a marine propulsion device and a communication device configured to perform communication with the server , wherein the marine propulsion device includes an engine and a controller , the controller being connected to the communication device, the controller is configured to encrypt data (D3) related to the engine with an encryption key associated with information (D1) unique to the engine , the communication device is configured to transmit the encrypted data (D3) related to the engine to the server , and the server is configured to receive the information (D1) unique to the engine , and the encrypted data (D3) related to the engine , the server being configured to decrypt the encrypted data (D3) related to the engine with the encryption key associated with information (D1) unique to the engine , characterized in that the controller is configured to control the engine and configured to encrypt an operating time (D2) of the engine with the encryption key associated with information (D1) unique to the engine , the communication device is configured to transmit the information (D1) unique to the engine and the encrypted operating time (D2) of the engine to the server , and the server is configured to receive the encrypted operating time (D2) of the engine , and being configured to decrypt the encrypted operating time (D2) of the engine an encryption key that is associated with the information (D1) unique to the engine , the server is configured to decrypt the encrypted data (D3) related to the engine with the encryption key associated with the information (D1) unique to the engine , and the server being configured to determine whether or not the decrypted data (D3) related to the engine are genuine based on the decrypted operating time (D2) of the engine . a server ; and a watercraft including a marine propulsion device and a communication device configured to perform communication with the server , wherein the marine propulsion device includes an engine and a controller , the controller being connected to the communication device, the controller is configured to encrypt data (D3) related to the engine with an encryption key associated with information (D1) unique to the engine , the communication device is configured to transmit the encrypted data (D3) related to the engine to the server , and the server is configured to receive the information (D1) unique to the engine , and the encrypted data (D3) related to the engine , the server being configured to decrypt the encrypted data (D3) related to the engine with the encryption key associated with information (D1) unique to the engine , characterized in that the controller is configured to control the engine and configured to encrypt an operating time (D2) of the engine with the encryption key associated with information (D1) unique to the engine , the communication device is configured to transmit the information (D1) unique to the engine and the encrypted operating time (D2) of the engine to the server , and the server is configured to receive the encrypted operating time (D2) of the engine , and being configured to decrypt the encrypted operating time (D2) of the engine an encryption key that is associated with the information (D1) unique to the engine , the server is configured to decrypt the encrypted data (D3) related to the engine with the encryption key associated with the information (D1) unique to the engine , and the server being configured to determine whether or not the decrypted data (D3) related to the engine are genuine based on the decrypted operating time (D2) of the engine . <EOS>