Thanks this is good information. I may have to give one of these diesels a try...The boat is a 29 foot Velocity VR 1. A go fast style. It sits fairly high has a small cabin. You can google it and get an idea. I would guess that it has less wind resistance then a boxy travel trailer. The 22 mpg is the combined mpg. I hauled the boat to Lake George and returned empty. Without the boat I usually get 28 to 29 mpg. Could do better but I have a heavy foot.
Padraig