RedactedNarrative: On 6/29/14, V1 was boating/fishing on the Iowa River and had motor problems through out the day.  They were able to fix the motor & return to the boat dock where they had launched. The owner of the boat went to get the trailer while the operator stayed in the boat, to load it onto the trailer. Before the trailer was launched the motor quit & V1 began to float downstream.  The Operator was unable to get the motor started again & approximately 400 yds from the boat ramp, the boat hit a log & capsized.  The operator fell out of the boat but was able to swim to shore.  The boat & motor sank.  On the day of the incident, the Iowa River was over flood stage with a flow of 15000 CFS.  Normal flow for the area is 6000 CFS.  The Operator was not wearing a life jacket.