What do you all leave as a reserve fuel capacity?

[serpa4]

Almost everyone says don't use all the fuel in you boat.
What do you all leave in the tanks percentage wise?
I've seen anywhere from 15-25% capacity. One article said only use about 66% and leave 1/3 of a tank in the boat for safety; that's a whopping 62 gallons never used!!!
So, a CW30 would have a "safe" route planning capacity of about 144 gallons(20%) x ~1.6 mpg cruise = 230 statue miles safely barring any wind/waves/current for range on a tank.

How much do you all leave in your tanks?
Thanks.

 

[Karll]

I wait until I am under 100 gallons in my 150 gallon tank as Cap Santa gives a discount on the fuel cost if you buy over 100 gallons at a time.

 

[Chimo]

The answer is "it depends".

First it depends on how far you're travelling from a refueling point. Second, it depends on what bad conditions could be encountered. Third, it depends on how much of a pain you find refueling.

When I was going offshore (not in a Ranger Tug!) the 1/3 rule applied. That was 1/3 out, 1/3 back and 1/3 for the Devil and what conditions he might dream up while I was out, usually unexpected bad weather.

These days I mainly do trips of 1-2 nights with exceptional up to 4-5 days around the Southern Gulf Islands or San Juans. I'm never that far from fuel and a full tank of 80 gallons gives me about 150 miles leaving 15-20 gallons in reserve.

Dropping by the gas dock on the way out of the marina is easy so most of the time I don't fill the fuel or water tanks. Why carry all that weight and fresh diesel is better than stale. I'll top up to about 60+ gallons and run down to 20. Again, I'm never too far from fuel if I need it. I know I am refueling about every 100 miles but to put that in perspective, that's Sidney to Roche and return (when it was allowed) three times.

 

[Red Raven]

I agree with David on Chimo. On our trip to Alaska we only ran below 30% one time and that was when we knew we would be near fuel at Petersburg. When cruising around Puget Sound I don’t worry about it as much but still generally fill up when we get below 30% or when the price is right! 😀

Curt

 

[scross]

In the PNW it’s easy to be safe regarding fuel levels. Seems like there’s diesel (or gas) at almost every marina in the San Juan’s. In the Gulf Islands and Sunshine Coast you need to be a bit more attentive to your fuel.
But, if you’re planning on cruising in the Gulf of California or up to Alaska like Red Raven, where diesel is only available every 200-250 miles or so, it’s a different matter!
I try to pull the boat out with well under 20 gallons in a 75 gallon tank to keep the boat light on the trailer. Otherwise I try to have at least 25 gallons in the tank between refueling.

 

[BB marine]

My C26 only has 80 gallon capacity. I pumped all the fuel out of the tank with the boat on a trailer sitting level. There is was 4 gallons of unusable 5% of 80 gallons. The fact that the tank is so hard to fill to full capacity I use 10% of the fuel is not usable. When calculating fuel range I use 20% for my numbers. I have 64 gallons of fuel giving me a range of 256 miles at 1850 rpm 4 mpg 6.5 kt , 211 miles at 2230 rpm 3.3 mpg , 2.6 gah 7.6 kts 8.7 mph, 115 miles at 3220 rpm 1.80 7.2 gph 11 kts 12.8 mph, 112 miles at 3550 rpm 1.75 mpg 9.1 gph 14kts 16 mph.

I did one fuel restricted trip on the Mississippi river to Ohio river to Kentucky lake total 239.7 miles between fuel stops. We had a full tank, plus 2, 7.5 gallon portable fuel containers. A total of 95 gallons of fuel - 8 gallons of not usable = 87gallons. My engine rpm was set at 1850. We gained mpg on the Mississippi strong down stream current. We lost mpg on the Ohio and Tennessee strong current as we were going upstream after a lot of rain from a Hurricane that went up the Tennessee valley. We used 60 gallons of fuel for this trip I had 35.7 a gallons left total in he tank -my 15 gallons of extra fuel = 20 gallons left - my 20% = 4 gallons left the 4 gallons of fuel would have theoretically taken me 16 more miles = 255.7 miles with 20% left 10% usable and 10% not. ( my MPG was right on all downstream advantage was lost with upstream disadvantage but the fuel average was spot on.)

I added an additional 22 gallon auxiliary fuel tank to the boat. I use 17.5 gallons as usable when I figure my cruise range. I now have a max cruise range of 326 at 1850 rpm and 142.6 miles at high cruise leaving 10% not usable and 10% reserve.

When fuel is availability is restricted is really the only time it is needed to calculate reserve fuel capacity. When it is not I use the 100 mile fill up as my rule. This leaves me at least 40 gallons of fuel on board.