Hi Colin,
The mounts need to be at this angle, as this is the rotational alignment which could require adjustment due to minor tolerances in the jet drive model. There isn't much access to adjust them so it will be ring spanners on both bolt head and nut (which will be in the inner side near the coupling).
The mounts will be bolted to the bulkhead with couplings screwed to the jet drive shafts, the motors then slid on the couplings and pushed up until the moving part of the motor mounts sit flush against the motor face which has the fixing holes. Once in place the screws Will fix the motor to the mount and (with the boat in a vertical position) the mounts fixed using the bolt/locknuts, the motors will then be perfectly aligned to the driveshafts and fixed in place.
Development and testing comes after the design phase, like with the Bofors Mini MK111