Fuel Tank Question

[capeguy]

My 2017 Canyon 306 (Yam 300s) has a 290gal tank according to GW specs. After taking a much longer trip than anticipated I got to the harbor with the lowest bar on the gas gauge flashing as a low fuel alarm. The four of us were curious how much was left in reserve at that point as I have never run it down that far. Turns out when I filled it, it only too 230gal! So a low fuel alarm and flashing bar with 60 gal remaining!

After burning 42 gal yesterday, I am down to 7 bars!

Does this seem normal to have that much of a reserve?

Seems to me, with 10 bars, each bar should be roughly 29 gal. But clearly the top bars are not that, and the bottom bars mean much more.

Anyone else see this or understand how to interpret how much fuel is left? I always reset my fuel consumption when I fill , so I can tell that way, but wondering about the gauge???

 

[seasick]

Were the four of you on board when you read the gauge prior to gassing up?
Although the sender is fairly accurate as far as level goes, it can't take into account the fact that the tank angle changes under different conditions such as trim or in your case perhaps loads. The sender also has a space between it;s lowest sensing level and the tank bottom. The gas below that level is what you called reserve and it can be a significant amount. Let's say your tank is flat and 10 inches tall. If the sender sits an inch above the bottom ( an inch is the recommended height) than 1/10 of the gas is not measured. In your case that is about 30 gallons if the tank were flat and level and it probably isn't. That means that 30 of the 290 is not measured, so your 'visible' capacity is 260. All that logic applies to a perfect world.
Also note that when one solid bar changes to one flashing bar, that means something but just noticing that one bar is flashing tells you that your level is in a range and that range can be more gas than you would imaging.
The point is not to rely solely on the gauge level. Your fuel management readings if set properly are much more accurate

 

[georgemjr]

It is EXTREMELY important to realize that there is a significant amount of gas that you will not be able to burn so although there were 60 gallons left in the tank, 30 of them could easily be unusable. I made the mistake of running my rear tank to empty (33 express), knowing that I had at least 30 gallons of gas in the front tank. Because the rear was empty the boat sat ass high, bow low and all 30 gallons went to the front of the tank. The pick up is at the rear. All 30 were untouchable and I had to get towed to my slip. I never burn the rear down completely, first. Even without changing the angle of the boat, the pick up does not access the entirety of the tank. There is always unusable fuel. That being said, my bars are generally accurate, each one being 1/10th of the tank capacity.

 

[DennisG01]

The gauges are consistent, but not always accurate. That is normal. It depends, largely, on the shape of the tank. This is true in many cars, too - it's just not something you ever really think about in a car. Every car I've had goes through the gallons faster once the gauge gets to about 1/3 or 1/4 left.

Do your gauges have (or do you have a stand-alone gauge) fuel consumption? You could start using that as that would give you an accurate representation of how much fuel you've gone through - and simple math would tell you how much you have left. Ultimately, the more you use the boat, you'll figure things out and get a comfort level with it.

 

[capeguy]

Thanks for the info, interesting. My Yamaha digital gauge does have fuel flow, both real time and cumulative. This is how I manage my fuel, by knowing how much I put in and how much I use. This was the first time, due to a conscious decision to go further, that we knew we were getting below the remaining fuel I KNEW we had from the last fill up, but I didn't know how much was in reserve with 1 solid bar. We figured at least 29 gallons if each bar is 1/10th, and then we figured we had some reserve.

After the 1 bar turned to a flashing bar, we got a little nervous not knowing how much we had. I didn't run it down to see that flashing bar stop, I assume that would be calibrated to be the end of usable fuel?

This "unusable" fuel concept is one I hadn't heard, but makes sense and is good to know. How would one plan for range? If I can cruise at 1.4mpg, what amount of fuel do I use for my range?? If not the 290 gal tank size, then ???

 

[seasick]

Your cumulative reading is the more useful. On my other boat I reset when I gas up. That way, if I added 40 gallons last fill up and now the cumulative says I used 40 gallons, I have left what I had before the last gas up. I think I made that sound more complicated than it is.
Every time you add gas, keep notes of how many bars were displayed sitting at rest before and after adding gas. Over time you will get a good idea of what the bars mean and what range a bar represents.
Next time you are out with your friends, note the bars at rest with all crew back at the transom and then again with all crew at the helm.
On my 208, shifting the passengers can make the display change by 2 bars. Getting on plane can change 3 or 4 bars!
Your question about what happens to that one flashing bar as you burn gas is one I can;t answer since I never let my gas get that low.
Perhaps someone else knows by real word test or by playing with the sender out of the tank.