The guy who writes about this stuff for sail magazine once did a comparison chart of cost per kilowatt hour for various sources with amortization of the total costs. The outlet at your marina is like 25 cents per KWH. Solar and Wind is a whole lot more, your main engine can run $5.00 per KWH! The hands down winner for low cost per KWH was the little Honda inverter generators!
I got curious and did a little research on the life span of those things. I found an interesting website by a guy who had been living in a house far off the grid using portable generators for power with batteries and inverters for night time use. He was getting about 1000 hours out of number of different brands before they required too much repairs to be worth rebuilding, and he was religious about proper maintenance. Then he bought one of the little Honda units, for about twice the price. After 5000 hours of really low noise operation he realized they were a bargain!
I was in a rental place one day and they had a long row of portable generators sitting there. I asked the guy if they had ever tried one of the Honda inverter generators. He said a salesman came in, but they were much to expensive. I explained to him that the typical rental generator gets taken to jobsite where it sits and runs at full speed for 8 to 10 hours a day, burning a lot of gas, making a lot of noise, wearing it self out, waiting for someone to pull the trigger on a saw or drill for a few seconds maybe 100 times a day. The Honda would sit there idling away, using little fuel, making little noise, and wearing very little. It would speed up as soon as the load was applied. I'll bet the contractors would love the low noise and small fuel use, and would even pay a little more for the Honda. So it is very likely it will last way longer in that service, easily justifying the premium price.