Hi Gus,
I didn't talk about all the features of the circuit yet.
Assuming that the aerator will be battery powered from the boat starter battery I added a battery monitor circuit which might be set to any voltage level (withing limits) making a motor start possible. (I suggest 11.5V at the threshold for safe motor start). The circuit drives an audible alarm circuit which is a buzzer with a self contained oscillator circuit (normally 2.5 to 3.5KHz)
The LCD background light might be set to any convenient level via menu and select buttons, The photo transistor is located in the "menu" button and senses sunlight intensity. With increasing darkness the back light will dim more and more to the level set by the user.
For normal operation the display will show the remaining times for the aerator activation time and the pause time in minutes and seconds. If any value is changed during a cycle the new value will automatically be used in the next cycle if the input has been done using the "INC" and "DEC" button.
If the new values should immediately be effective the "ENTER" button must be pressed. (Resets the down counters and loads the new values, starting with an active cycle)
Talking about proper soldering I just mean not to use a plumber's iron which is used to make gutters and fall pipes, but a temperature controlled iron, a reasonably fine tip (e.g. chisel of 1.5 to 2.5mm) and thin resin (flux) core electronic tin (not thicker than 0.5mm (~0.02"). I use tin of 0.35mm thickness and use it sparingly. Too much tin won't make the joint stronger.
I was invited to a school class where simple circuits were put together off a kit. There was just one circuit out of 24 working at all. The PCBs, although professionally manufactured with solder stop layer looked like a plumber had done his work.
Additionally all boards were covered with an ugly dark brown pattern of melted and half way burnt resin leftover.
So I take the mentioned board dimensions of 3.225X2.5" being granted.
Regards
Boncuk