Sunset Dream Fuel Economy
IMPORTANT: ALL data in this section has been WILDLY estimated. While tracked to the best of my ability, results could be off by as much as a factor of two or more.
DATA Collection Method:
Sunset Dream has a sight tube for each of the port and starboard fuel tanks. To allow for data collection, rulers were secured behind the sight gauges, so that approximate readings could be collected. Sight gauge readings were taken along with recording the values on the port and starboard engine hour meters. Sight gauge readings and hour meter readings were collected immediately before and after both fuel purchases as well as the amount of fuel purchased (in gallons).
The first (and only) fuel data point at this time was calculated using values from the first fuel purchase to the second fuel purchase.
INACCURACY in data collection may result from the *assumption* that the fuel tanks are regularly shaped, and that the volume of fuel is linearly related to the level seen on the sight gauges. Baffles and other structures in the fuel tank will affect this. As the shape and construction of the fuel tanks is obscured, we do not know how good the assumption is of the fuel level being linearly related to the sight gauge reading.
Readings of the sight gauges are taken by photographing the sight gauge level. Height and angle of the camera (phone) when the photo is taken, as well as the interpretation of the reading level, will affect the accuracy of the readings.
We *assume* that the volume of fuel purchased is accurated reported by the fuel pump.
The engine hour meters appear to be reasonably accurate.
Note that the fuel burn rate will vary, and may vary dramatically from idle (time at the dock, and while motoring in the marina) to cruising speed, to high cruising speed.
FOR PURPOSES OF THIS DOCUMENT - we will assume an AVERAGE CRUISE of about 1500-1600 RPM, at about 7Knts/Hr.
The second fuel purchase was at Blue Marlin Fuel Dock on 8/12/23. 85 gallons of diesel was purchased - 50 gal in the port tank, 30 gal in the starboard tank (note that tanks are kept at different levels to assist in balancing the boat, as the boat naturally tends to list to starboard). Based on the sight guage readings immediately before and after the purchase, an *ESTIMATE* of about 8.5 gallons/inch on the sight guage was made.
Using the data from the previous fuel purchase, current fuel purchase, and hours of engine operation, an ESTIMATE of approximately 2.3 gal/hour was determined. CLEARLY, more data is needed to give any statistical validity to this estimate.
At time of purchase, the data reported in the boat purchase listing suggested that the boat had 400 gallons of fuel capacity (two tanks [port and starboard] of about 200 gallons each). Based on the data collected so far, it appears that the actual fuel capacity of the boat is closer to 200 - 240 gallons total (not per tank), based on a reading of 14" on the sight gauge. The tanks clearly have capacity above a reading of 14" on the sight gauge. Unfortunately, it is not known how much fuel capacity is above the 14" reading, and no attempt will be made to take advantage of that capacity, as calculations will not be possible in that range.
Due to concerns about what sludge may be at the bottom of the tanks, I will generally be disinclined to run the fuel level below 4" on the sight gauge. This provides about 10" of useful range per tank, resulting in a total of approximately 170 useful gallons.
Assuming approximately 3 gal/hour burn rate (conservatively), at about1500-1600 RPM, at approximately 7 knots (8mph) => This yields a total estimated range of ABOUT 400 miles.