I installed a FloScan fuel management system on my boat that I re-powered with a 4 cylinder turbo'd Yanmar 4LHM-STE 230 hp diesel . I installed the diesel 8 years ago after putting 1200 hours on the gas engine. I sold the gas engine and tranny while it still ran well but was becoming a bit noisy.
In the 8 years of running the boat with the diesel, I never knew, not even close, what my miles per gallon truly was at any given speed or engine RPMs. With the FloScan now installed (by myself) I can now determine that I can realistically get 6.15 nautical miles per gallon (FloScan always reads GPS data as nautical) @ 1,370 RPM. Speed over ground is 7 statute MPH, + or - 0.2 MPH. That is my absolute maximum MPG as determined by my observations by adjusting my RPMs and speed upward @ 1,000 RPM increments and writing it down in my log book. The calculations are done by the FloScan instrument's mini computer that receives info from my GPS plotter and so, real time updating is constantly being digitally displayed and the info ...RPMs, SMPG, engine hours accumulated and gallons consumed since refill are all real time current and relative to your time and distance on the move.
I would have never had the patience to go 7 MPH (in my 31 MPH boat) for any necessary length of time to make the determination that my maximum range and MPG is specifically at 1,370 RPMs. The beauty of it all is that to arrive at that determination, I only had to set the boat on autopilot and on calm waters, observe the data reported by the LCD display on the FloScan instrument which delivered the data within 30 seconds of my adjusted (set) engine RPMs. You have got to love it and after experiencing it you will.
June 13th my boat leaves St. Pete for Chicago on a flat bed semi rig just so I can do another rivers trip from the Great Lakes to my St. Pete water front (ICW) home. I keep my 1976 restored and customized 26' Silverton on a lift at my home. When I bought the boat in Milwaukee back in '91, it had anti-fouling bottom paint on it. I ran the boat down the rivers then and finally, after all these years, the bottom paint was almost washed off. With a pressure cleaner, I blasted off almost all of the remaining loose and degraded bottom paint and with the boat on the lift, I painted the bottom with a polyurethane paint that makes the bottom a shiny, hard "fast" bottom. Since the boat is always on a lift when not moving, I figured why not a fast bottom to see what effect it would have on my MPG and speed. The result is startling.
I had the boat out for a trial run and @ my upper end cruising RPMs, my MPH has increased by 4.7 MPH! My SMPG appears to have improved by 0.7 NMPG! All of my previously recorded observations will now have to be re-recorded, as the performance and efficiency has, without a doubt, improved.
A word about fuel management system choice. Before I buy any electronics for my boat or home, I conduct a "performance test" of sorts on the seller and or manufacturer's sales and tech support. My first priority is make sure that in the case of a problem, I can reach the seller's/manufacturer's sales and tech support by phone. I was able to do this easily with both Raymarine and FloScan. No hoops to jump through. Just called the support number and began talking with a rep immediately....and that was before I even purchased the item! No one ever asked my for documentation of a purchase so as to qualify me for a dialogue.
A word about installation. I did install the FloScan myself, as well as the diesel engine and Raymarine plotter. I have had extensive experience in rigging boats and internal combustion engine maintenance and repair. I am capable and confident with a history of installations of all kinds that make me so. If you are similarly experienced and confident, go for it. FloScan has a free video CD that explains the function more so than actually demonstrating the installation.
I have to give both FloScan and Raymarine high marks for their accessibility when needed.