I have a 80 model 43'FBDC with DD671 N's, I think J&T rated at 310hp. WOT is a honest 2500 RPM which is what they are rated for under load. My question is at what RPM would this boat need to run to be the most efficient under the following circumstances? I will be going upstream on the Miss. R. here in Memphis about a total of 310 miles without a fuel stop. I carry 275 gallons in the aft tank and in a forward tank 90 gallons. I intend to carry two 55 gallon barrels as well. With the current here around 8 to 10 mph this boat seems to run better at around 2200 to 2300 upstream. I can back down to around 2000 which requires a lot more effort to steer against this strong current which I think due to the large keel these boats have. Whats the difference in fuel consumption at these deferent RPM"S and any other thoughts about a running speed. I think at 2000 I am making about 10MPH and at 2300 maybe 12MPH. There will be 4 adults on board with enough stuff for 4 days. tuned props and a clean bottom just painted. Thanks