Next on the list of factors is pressure. When you increase the surrounding pressure, you can usually dissolve more gases in the liquid. Think about your soda can. It is able to keep the fizz inside, because the contents of the can are under higher pressure.
Assuming a prop, it depends on how you are propped but with a redline of 6000 rpm, most outboards perform best with a cruise in the 4000-4400 rpm range. If you want top fuel economy, get a floscan or such and see what is the most efficient for your engine and prop.
You want a filter that has a flow rate of about 60 gph to avoid a fuel restriction as the filter fills up with debris even though your engine consumes a good deal less than 1/4 of that flow. 2 micron is way too small for an outboard motor and is not recommended by any outboard motor manufacturer.