A failure prediction system having small boats operable by operators, each mounted with an outboard motor equipped with an engine and an Electronic Control Unit and a computer located in a land office connected to the ECU. The ECU acquires boat ID assigned to one small boat on which one operator boards and his personal ID, accesses the computer to acquire past manipulation data of the acquired personal ID for all boats, acquires manipulation data of the one operator during current run, merge the data with past data to generate merged data. Then, it select a parameter in the generated data and set a normal value range by the parameter, assesses whether parameter in the data during current run is within the range, and determines the outboard motor mounted on the one boat is in failure when the parameter is out of the range.