Welcome
@MPaul to the SBO forum and sailing the SALISH SEA.
Sounds like you have been around a bit. Good on you. Sidney is a sweet harbour to be out of. Sailing means no worry about fuel capacity.
The 20 gallons means at least 20 hours of cruising. 35 gallons means more.
Perhaps the 20 estimate was imperial gallons while the 35 number is US gallons.
In the Americas, a gallon is equivalent to 128 fluid ounces or 3.785 liters. But in the UK, it's 160 fluid ounces or 4.546 litres. That's quite a difference, with the British contenders having to potentially 20% more fuel than their American counterparts.
Now that could mean 24 US gallons not 35. So the extra must be a measurment error.
It would not take long to rumage about the boat and do the mesurement math... Or your could consirer 20 hours at 6 nm an hour would be 120 nm. That might be enough diesel to get you from Sidney to Otter Cove at 1 gallon per hour. On the off chance that you had the tides with you and the engine tuned you might find the miserly fuel consumption could get you there and possbily back on a full tank before you untie the lines.
And wind (and we know the wind might blow in the Georgia Strait or the North waters of Vancouver Isle and the currents will flow)... you might arrive back in port with a reserve of fuel.
It is not so much the size of the tank but the way the skipper considers using the fuel they have.
Good to have you aboard. Look forward to see you on the water.
