I have done over 50 miles round trip out on the Great Pacific Ocean from San Francisco Bay. The day was glassy with no waves and we could make top speed, but tended to keep it around 18-22 mph. Burned a full tank of fuel 6.6 US gallons, and had to plug my 3 gallon reserve tank in as I ran out as we entered the Marina.
When on a boat for along time I have to get comfortable once in a while. That means standing up often. I will sit stand on my motor, and typically I have my launch wheels on to lean against. If there are only a couple of us, or myself I bring a camp chair to hang out in and relax. Since it supports my back it is more comfortable.
On that note, I did buy a small folding boat seat and have been contemplating bending up some tubing and instead of sitting on the hard tube sit just above it on my new seat. Never seen it done before?? If that great idea doesn't work, I am going to build a bench seat and mount it on that for when I have only one passenger. I plan to do that anyway. Got a few projects before either one comes about though.