RedactedNarrative: Operator stated his trim tabs were not working well.  He noticed boat would not get up on plain and observed vessel taking on water so he ran vessel on a sand bar south of deer island before boat completely sank.  Was determined a bracket seal plate on motor mount bracket was missing that caused boat to take on water.  Operator also stated automatic bilge pump was not working.  Motor and electronics on vessel was damaged.  Estimate damage was $25,000.  Passenger cut his foot on something in back of vessel and received stitches at urgent care.