Boat scetch:

Assembled drive:

Notes:
Large dia propeller = 16"
Steering by small 24V dc motor and tooth belt
Cooling fan inside larger belt wheel
Motor is Perm 132

Mariner-Yamaha outboard 15hp rig:

Electrical steering system, steering motor disassembled:

Motor and larger tooth belt wheel for steering:

There is a cooling fan inside the wheel

Unit less steering bearings an rig outer tube:

Adapter to outboard motor rig lower part:

Rig:

PVC tilt-up cylinder. Rig tube rotates 360n deg. in the cylinder hole:

Fan inside steering belt wheel:

Cylinder assembled to boat hull (hull stern mockup):

Note: The white box demonstrates a slot at boat hull stern.

Motor rig at cruising position:

Note large diameter propeller for good efficiency.

Motor rig tilted up: