If you were asked "Did you checked the outdrive?" by an investigator during a boat accident, what does it mean

The outdrive is the propeller portion of the drive mechanism of the boat. Damage to the outdrive would indicate that it hit an object in the water which could cause the boat to veer off course or capsize. It could be the difference between an accident versus negligence on the part of the boat operator. If the boat accidentally hit something causing the accident then the boat owner would probably have no criminal liability. If it was gross negligence then there is criminal liability.

Good point Jim C. That would support the gross negligence assumption if it wasn't properly maintained and contributed to the accident

The outdrive is you lower unit coming out of the back of the boat, actually propeller and lower unit. Apparently the investigator was inquiring as to whether you checked that area for damage or something/someone.

Assuming you have an inboard/outboard motor (engine inside, prop outside) on your boat, the "Outdrive" is the portion of the motor that is outside the vessle - usually meaning the prop and lower unit.

If they're asking if you checked it, they want to know if it was in proper working order prior to the accident. Things such as the motor tilted properly, turned properly, sucked in water properly - things like that.