I posted this link as a response to a question regarding fuel consumption in a 502 motor. You can select from different motors as well as single or twin engine setups. The app is nice and can give you a ball park number for gph used as well as Mph. The rpm guage will move giving you the GPH numbers. On the MPG page you put in your speed at rpm and it will give you and est on mpg you will have. Not exact but I think it would be a good planning tool for those wanting some fuel consuption numbers.

MerCruiser 8.2 Fuel Consumption 430 HP | MPG GPH US Gallons per Hour | Mercury Magnum HO 502 v8

Kool..... Thanks for the link