If the engine can tolerate a lower oil level in rough seas, it could likely do so in calm waters. The biggest consideration is having reserve capacity to deal with consumption loss, and enough capacity to handle cooling. The first part you cant do anything about without modifying the pan as I wrote earlier. The second case could be monitored with an oil temp gauge. If your changing oil by vacuum, next time its empty you could pull the sump plug and find a thermocouple to fit the thread, or via an adapter. Alternatively you could monitor the sump with an IR heat gun. 200F is about the max you would want to see.I’ve also learned that I probably need another 1/8 inch down on the dipstick as a safety margin in water rougher than I usually let myself get into. I’ll probably run with higher oil in the smooth water of the ICW but I’m going to be sure the oil level is proper before facing open water.
The other interesting thing I learned is how an engine will continue to produce high crank case pressures and oil filler blow out for quite a while after a foaming event. It takes overnight and some heat for things to calm down.
Interesting about the time to settle the oil. What kind of oil are you burning?You may want to look into an oil with better anti-foaming properties, or an anti foaming additive. Your know your bound for some rough waters again.
I would do something to that stick to permanently remove the current marks and put a new mark on it where it needs to be, so there is no more confusion.