From JH
Hi Andy, the main purpose of the hatch is as an escape hatch for the jet space
- in case of fire, flooding or pyrogen discharge in the engine compartment (the standard access route)
The jet space is separated from the engine compartment by a watertight bulkhead with an acces door
The possible reason for a crewmember to be in the jetspace is to be able to manually control the buckets and steering nozzles by mechanical means in the event of a total failure of the electronic controls and the back up electrical controls.
The other reason to access there would be in the case of impellor fouling
As there are inspection scuttles /hatches that can be opened with the boat afloat (with everything stopped!) as long as sea-state is moderate to allow an attempt to physically remove or cur away whatever is fouling the impellor - (assuming that the normal control procedure of carrying out a back-flush by engaging reverse gear to drive the impellor in reverse has failed to clear the fouling)
As for opening the hatch the internal opening lever is permanently fitted, and you are correct that there is a removable
key/lever that is stowed just inside and to the right of the wheelhouse door