WARNING
Like an automotive cruise control, the PowerTroll is not an autopilot. It will not get you from point A to point B. It will not follow a course. You can't leave the driving to the cruise control! It will run aground, run into other boats, or otherwise get you into serious trouble if you choose not to pay attention to what it is doing.
Furthermore it is subject to a variety of failures. You must not use it in circumstances where you are unable to immediately resume manual steering of your boat.
It will, under good conditions, hold a heading for you while your hands are busy with other projects. But your eyes and attention still can't wander far or for to long from what your boat is doing.
Operation is limited to low speed (ie, trolling). Since the device has no throttle control it can't anticipate the change in helm effect caused by higher power.
This is not a commercial product. It is not 'engineered'. It's hacked. There is no warrantee of any kind on anything (hardware, software, parts, instructions, advice, ...) you get here. I make no assurances you will be able to successfully construct and operate this device. If it doesn't work it's up to you to figure out why and fix it.