Estimating fuel reserve?

[wrasse]

My 24ft donzi's fuel gauge is nortoriously inaccurate and my understanding is that most boat's are. I believe my tank holds around 80gals. I've been too chicken to go anywhere far on the water due to fear of running out of gas. Instead, I do one day cruises around my lake and fuel up each time I go out. But I really want to go exploring places further away and be confident in how much fuel I have left.

Any suggestions?

[pmreed]

Resist the temptation; don't fill it up after your next run. Don't get too far (like a 1/2 hour run) from a gas stop next time out. When the gauge starts to bump, get gas at your next available stop. Most of us have a good idea how long we can run on a tank and treat the bumping fuel gauge as you treat the reserve light in your car. Keep track of the distance and hours run too on that tank. When you fill up, you'll know how much was left in the tank and have a good idea of your consumption.
Phil
Of course, that assumes your gauge is working. If it's not, you'll be looking for a tow.

[RedDog]

Confirm your tank size. If you have a single in the 24, which I suspect is a Ford 460, you should be able to venture 200+ miles at a reasonable cruise with occasionable but limited high speed spurts.

Plus, since you have refueled each time, you should have a baseline of understanding of just how far you can go - assuming you DO know your tank size. If your outing around the lake takes 40 gallons then 2 laps around is good

[wrasse]

It's a 454 chevy. I really don't see the fuel gauge move off "full" until I burn at least 25 gallons. I think I have 80gals but not positive. I want to head out to san juan islands around here but I'd like to improve my understanding of my fuel reserve situation first. Maybe carry extra fuel on board?

[Formula Jr]

Two five gal portable gas tanks will get you to any port with gas in that area if you run out. If you have a gps you can readily tell what your crusing distance is on Lake Washington just by filling up and then crusing around the lake till you are near empty. You can do this over the coarse of several outings and add up the mileages to get a total. Friday Harbor is about 70 miles from Seattle.

What you really want to do is calibrate your gas gauge. And then you will know what the tank is holding on any particular reading. If it registers as full and you have to burn off a lot gas to get it to start moving, you will need to know what that interval is till it reads less than completely full. Then you need to know how fast it drops once its off full.

My G30 van with a 454 has a 40 gallon tank. Gets 10 MPG towing at highway. But the needle doesn't even move off full till I've gone 200 miles. So I have half the distance left once the needle starts moving. Once it reads 1/4 tank, I really only have three gallons left in the tank or 30 miles to find gas.
I mapped how much I needed to add to the tank at the various places on the gauge. This gave me a true calibration.

[Dr. Dan]

:wink: I agree with alot of whats been said.... but the most accurate is to:

1.) Confirm through Model and Manf. your Fuel Tank size

2.) Install a Fuel Flow Meter, this will track the consumption burn of what you are carrying, and you will know exactly what you have to burn from your last fill up!

3.) When I get bored, we are going to install some flow scan items on our puddle jumper.

But for now I use the 1/3 of a tank Out, 1/3 Return and 1/3 as reserve rule... it gets me around the Chesapeake Bay just fine....

Good Luck

Doc

[BigGrizzly]

I like Doc's idea. Typically they get 2->3 mpg on a cruise.

[Formula Jr]

Just to ease your concerns Wrasse, once you've established that you indeed have an 80 gallon tank. Heading to the San Juans from Lk Washington with a full tank gives you a very wide safety margin. You can't go out and back from Seattle to the Islands on one tank. This is "range;" but you can easily get to any of the many gas stations on the Islands even if you are running against the tide and wind. Expect to be shocked at the pier gas prices on the islands. They have to ship that all in using tanker trucks on the ferries.
You could take smaller steps at first also. Like running to Blake Island and back or circling Bainbridge Island. That's completely with in your range of one full 80 gallon tank. The whole Sound has Cell Phone coverage if you get in trouble.

[MOP]

More than agree with verifying the tank size thats the biggy, now a simple idea fill the tank start up and go for a ride 1/2 out make a U turn back to the gas dock and fill back that way you will know just what it burns in 1 hours time!

Phil

[wrasse]

That's good to know. Haven't ventured out of the familar waters around lake washington yet but I really want to go via ship canal to explore puget sound. Is blake island/bainbridge a nice place to boat? Looking for a destination to visit and maybe dock there to stay overnight at a hotel near the water. I'd love to hear your recommendations on good boating destinations in puget sound! Good to know there's cell phone coverage just in case!



Just to ease your concerns Wrasse, once you've established that you indeed have an 80 gallon tank. Heading to the San Juans from Lk Washington with a full tank gives you a very wide safety margin. You can't go out and back from Seattle to the Islands on one tank. This is "range;" but you can easily get to any of the many gas stations on the Islands even if you are running against the tide and wind. Expect to be shocked at the pier gas prices on the islands. They have to ship that all in using tanker trucks on the ferries.
You could take smaller steps at first also. Like running to Blake Island and back or circling Bainbridge Island. That's completely with in your range of one full 80 gallon tank. The whole Sound has Cell Phone coverage if you get in trouble.