Maybe I can help you find out what your options are. What isn't clear to me from your description, is what kind of steering system you have.
Reading your post, it seems that you have added an Intellisteer drive unit and a remote controller (handheld unit and a receiver) to your existing steering system. Depending on the steering system, Intellisteer seems to sell different drive units and all of them seem to be labelled something 'octopus'.
I have looked up your 2006 Grady white 208 and it seems to normally come with a cable steering system, on the other hand you talk about an 'octopus pump' which suggests that you have a hydraulic steering.
The drive unit for the cable steering requires a clutch and the Nav Pilot 300 would not be suitable for it.
If, on the other hand you do indeed have a hydraulic steering system, you be be fine with the Nav Pilot 300.
The hydraulic drive that comes from Intellisteer is just a standard reverseable pump which sits parallel to wheelpump and drive cylinder. It doesn't need a clutch or bypass valve. And I would guess, that in this case the clutch output of your receiver unit isn't even connected, but do check the cabling on your receiver and if you find clutch wires check where they are going.
There are hydraulic steering systems that have two drive cylinders for redundancy, one used by the autopilot and the other by the regular steering. I that case bypass valves that are activated via the clutch output of the autopilot are necessary. I don't think your boat would have such a system though.
Looking at their (IntelliSteer) manuals, which are not very detailed, it seems the receiver unit would simply pass through drive and clutch wires from its input to its output when the remote is switched off. With the remote on, it would cut the input lines off, power the clutch output with 12V and take control of the drive wires. If the drive has no clutch, then no clutch wires are needed.
So I think that if you have hydraulic steering, all you need to do is to connect the autopilot drive wires to the receiver appropriate receiver input and it should work.