Fuel gauge location
- Thread starter Seb6226$
- Start date
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 23,179
If you have a plastic tank and can see the fuel in the tank.
You can shine a flashlight in to the fluid portion and the level of fuel in the tank will be revealed as the light bounces of the surface of the fluid. No measure the fluid level in inches. Measure the height of the tank.
Device the tank height into the fluid level anf you get the percentage of fuel in the tank. Check the tank volume (usually in gallons of liters on a tank label. Sometimes embossed in the plastic.) Multiply the total volume by the percentage and you have the number of gallons of fuel.
Once you know the fuel level you can begin recording the hours and compare against the fuel volume consumed. Generally .5 to .7 gallons per hour of engine run time. Using the hours of engine run time you can accurately estimate your fuel level. It will be more precise than any gauge you can install.
You can shine a flashlight in to the fluid portion and the level of fuel in the tank will be revealed as the light bounces of the surface of the fluid. No measure the fluid level in inches. Measure the height of the tank.
Device the tank height into the fluid level anf you get the percentage of fuel in the tank. Check the tank volume (usually in gallons of liters on a tank label. Sometimes embossed in the plastic.) Multiply the total volume by the percentage and you have the number of gallons of fuel.
Once you know the fuel level you can begin recording the hours and compare against the fuel volume consumed. Generally .5 to .7 gallons per hour of engine run time. Using the hours of engine run time you can accurately estimate your fuel level. It will be more precise than any gauge you can install.
Keep in mind that your fuel consumption will be highly dependent of variables, some of which you control, some of which you can't. Fuel consumption for a monohull is greatly impacted by your speed through the water (and hence rpm) As you approach "hull speed" for your boat it takes more and more power (and thus fuel) to go incrementally faster until you throttle up to max rpm. Throw in hull and prop fouling, current etc and it gets complicated.
My Hunter 40.5 LOA with a 33.33 ft LWL (Length at the Water Line) has a theoretical Hull Speed of about 8.08 Knots.
My calculated fuel burn at normal cruising 2500 rpm (from Yanmar 4JH2E Performance charts) is .99 gph and the actual measured speed achieved with a clean hull and prop is 6.5 kts with a calculated range of 232 NM on 35 gal of fuel (40 gal tank with 5 gal held in reserve) Lots of variables like clean hull, current, headwind etc can effect this.
At 3300 rpm, my calculated fuel burn is 2.08 gph but my speed only increases to 7.6 kts and my range is only 128 NM.
So, you can see that how you operate your boat and how consistent you are in operating is important in using the fuel burn rate to calculate volume. You should log every time you put in fuel, generally how you have operated (like cruised for X hours at Y RPM etc) so you can hone in on calculating your fuel used vs operating hours. Keep good logs on this or a separate fuel log. I do that and I also have an "engine performance table" I created that shows a lot of data.
Sorry, I'm an Engineer and a "Marine Engineer" to boot plus a Navy Nuc so I'm am a little too anal about these kinds of things. You'll have to excuse me
My Hunter 40.5 LOA with a 33.33 ft LWL (Length at the Water Line) has a theoretical Hull Speed of about 8.08 Knots.
My calculated fuel burn at normal cruising 2500 rpm (from Yanmar 4JH2E Performance charts) is .99 gph and the actual measured speed achieved with a clean hull and prop is 6.5 kts with a calculated range of 232 NM on 35 gal of fuel (40 gal tank with 5 gal held in reserve) Lots of variables like clean hull, current, headwind etc can effect this.
At 3300 rpm, my calculated fuel burn is 2.08 gph but my speed only increases to 7.6 kts and my range is only 128 NM.
So, you can see that how you operate your boat and how consistent you are in operating is important in using the fuel burn rate to calculate volume. You should log every time you put in fuel, generally how you have operated (like cruised for X hours at Y RPM etc) so you can hone in on calculating your fuel used vs operating hours. Keep good logs on this or a separate fuel log. I do that and I also have an "engine performance table" I created that shows a lot of data.
Sorry, I'm an Engineer and a "Marine Engineer" to boot plus a Navy Nuc so I'm am a little too anal about these kinds of things. You'll have to excuse me
Also, if you want to get real accurate on marking the tank level if you have a plastic fuel tank. Since the tank is probably not square (mine is not) you can empty the tank. Then fill in 5 gal increments and mark the level for each increment. Of course how much can actually draw out of the tank is also dependent on how far the fuel pickup tube goes down into the tank.