Range and Fuel Consumption?

[HannahB]

Looking for some input on "non-classic" estimates on standard burn rates for a merc 225 EFI hung on a 1998 21SC with worn bottom paint. I have 95 gallons and do not have a flo-scan device (yet). Any thoughts on my range, or thoughts on ways for me to best gauge my range for a day offshore? I would estimate average cruising to the grounds at about 28 knots, given average sea state. Thanks.

[HannahB]

All set- got it approximately figured out this weekend on a 176 mi. trip.

[bj]

What kind of figures did you come up with? I have a 2003 21' with 200 Merc efi and it seems that fishing, cruising etc I always get about 2 mpg. So far I have about 205 hrs and no problems at all.

[HannahB]

About the same from my best estimates. My average cruising speed to my southernmost point on Sunday was probably a little lower than I estimated, more along the lines of 26-27 knots. Trimmed properly at that speed, the ride was most comfortable and the boat "felt" most fuel efficient relative to RPM's (which I recall being in the 3800-3900 range) I guess I will plan on having about 200 miles of range for a day offshore (carrying along an extra 10 gallons or so for piece of mind). I apologize as I am not really super anal about tracking all these numbers precisely, (A floscan would be nice, to see what you're burning-up, but I can't imagine that my performance would be much better using those numbers, as opposed to using "feel" for how the boat is performing) And I just need an average baseline to work with to plan my days. The engine is extremely powerful and easily pushes the 21 at 50MPH when its FAC, but you pay for that power at 2 mi / gallon. It has a slight shudder in the low-range, but my mechanic tells me it's very normal for those engines on the low-end, and that mine is actually quite smooth, from his experience. Next engine will be more performance-enabled/oriented, but I hope to run this beast into the ground before that purchase.

[ocuyler]

You may find that installing a Flow Scan or Navman fuel flow meter may reveal some interesting things. For example, the most fuel effecient RPM/speed may have a range from 3600 to 4200, depending on conditions. Further, if you do get low on fuel, you know the EXACT amount of fuel remaining and adjust speed to be sure you get home. Personally, I think it's important to know your fuel consuption at hull speed/7-9 MPH, as it may save you a tow someday.

[HannahB]

Agreed, and I see where that can be helpful. But, I do think that you can get a pretty good sense for where the boat will perform best, given current sea-state, with some experience behind the wheel. I guess the Navman would confirm or deny that theory. I use baseline numbers to set up my trips, keeping a "conservative" range for the day, but I can see where being able to use an extra 10 or 15 gallons could certainly come in handy. It is on the wish-list.