18' Outrage - "Usable" fuel in 63 gallon tank

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Author Topic:   18' Outrage - "Usable" fuel in 63 gallon tank

Buckda posted 06-26-2008 04:04 PM ET (US)
In the past, there has been discussion on this site regarding exactly how many gallons of fuel are “usable” in a tank. A prudent skipper observes the rule of thirds – a third to get you out there, at third to get you home and a third of the tank in reserve; meaning it is difficult to really have an accurate idea of exactly what your boat’s range is on the main fuel tank.
This past week, I had an excellent opportunity to determine exactly how many gallons of fuel from my 63 gallon capacity belly tank (1986 18’ Outrage) were “usable” to help me get to my destination. Equipped with a 27 gallon auxiliary tank in front of the console, I set off on a fishing/camping adventure in the wilderness of Lake Nipigon in Northern Ontario, Canada.
Here is what I discovered:
I pumped 228 liters (or 60 gallons) into the tank after running out of gas. Meaning there are about 60 “usable” gallons in the tank with 3 gallons remaining that cannot be efficiently used by the fuel pickup tube.
I ran 40 miles at about 4 mpg after the gauge was fully rested on E. So when the needle was resting on “E” pretty solidly (i.e. not sloshing to E), there are about 13 gallons in the tank and about 10 gallons of usable fuel left, if you have the standard mechanical dial gauge.
*NOTE – my gauge has been replaced with a newer one from e-components.net, but the only noticeable difference was that the new gauge uses a synthetic float and the original gauge used a cork float.
This was mixed running, averaging 4 MPG (240 miles traveled on the GPS, divide by 60 gallons), including a fair amount of cruising at 2,800-3,200 RPM, some rough water operation and “trudging” and a considerable amount of idle/trolling, with a heavily loaded boat. Your mileage will vary depending on the motor and load.
In my earlier calculations, I had been using an estimate of 58 usable gallons and 3.5 mpg economy to calculate my range for planning purposes. I think those are pretty fair and conservative numbers now. Moving forward, I will keep the 58 gallon figure but round up the economy to a “getting more accurate” 3.8 mpg to try to have less slush in the calculations.
Incidentally, the penalty for running faster is severe. On the auxiliary tank, I ran 3,200 RPM for 40 miles and then 4,000 RPM for 46 additional miles and ran out of fuel at 86 miles and 25 gallons used, which dropped my economy to 3.4 MPG. Important to note in these days of expensive fuel prices.

tomol posted 06-26-2008 06:33 PM ET (US)
Good to know. I've always wondered how far I could go in "E". I knew it was a long way, but 40 miles...
Now to the important stuff. Where are your story and pictures in the GAM?
Buckda posted 06-26-2008 07:03 PM ET (US)
Half of the trip is recounted in the Trips/Rendezvous section under Lake Nipigon. I also included a link to photos (Check out my 42 inch Northern Pike!). The other half of the story is still in development. I had to go back to work and haven't had a chance to finish it, but will soon.
Dave
TransAm posted 06-26-2008 07:47 PM ET (US)
I need to go through that exercise, but my tank is 140 gallons. It would take me almost $700 to find out and I have no reserve tank but for a couple of 5 gallon red cans. My luck, I'd run out of gas in [a notoriously small town]. Maybe my next trip to Ocean City.
Tom W Clark posted 06-26-2008 10:59 PM ET (US)
I know the useable fuel capacity of the fuel tank in my Revenge 25, it is 140 gallons, the specified capacity of the tanks in the classic 25 foot models. I know this because I ran the boat dry one time when I first bought it.
Interestingly, I noted that the placard on the Florida Marine Tank itself, located under the fuel gauge cover, says the tank capacity is 142 gallons.
alfred posted 06-28-2008 06:48 AM ET (US)
That is good info. I took it down to 10 gals once only, but normally fill when I am down to 20 gals.
Jerry Townsend posted 06-28-2008 02:44 PM ET (US)
Hey guys - careful. That is - the capacity of a tank is just the "nominal" capacity - the actual capacity may be more or less. Also - all fuel tank gauges were not created equal. All fuel gauges are not linear - some will fall off the "top-end" at a rate different from the bottom end.
And remember - that gauge, even if accurate, is only giving the correct level when the boat is level - and not on plane or moving.
I guess, what I am saying, is that running out of gas in the boat is not my idea of having fun - so make sure there is plenty on board. ------ Jerry/Idaho
Buckda posted 06-30-2008 04:08 PM ET (US)
Thanks for that Jerry - you're right. My post was simply to provide an example of approximation for other 18' Outrage owners so there could be some kind of comfort level with the fuel guage, which I almost always fill up once it get's near 1/3 tank, because I simply had never run it dry and didn't know.
On a related note, I had replaced the fuel/water separating filter right before this trip with a new one, and last weekend, I dumped the contents of the new filter to determine if there was any water in the bottom of my tank, and to figure out if the dregs of the tank came up through the fuel pickup hose when the tank was run dry. As I've said, I have not ever drained the tank in this fashion in my ownership of the boat, and I really didn't know if I had water/ethanol problems in the tank, or what kind of debris is in there. I do know there are two bolts in the tank, because I've dropped them into the tank when installing the gauge. I also know there is a small screw in there, because I also dropped that into the filler tube when attempting to connect the chain on the filler cap.
Anyway, here is what I found when I dumped the filter:
No water in the fuel(this was not unexpected, I buy highway gas for the boat almost exclusively except for a few big trips each year).
Also, there was a fair amount of rust. Since the tank is aluminum, I'm thinking that the bolts I dropped into the tank are disintegrating and resulting in some rust at the bottom of the tank. The filter is catching most of it (I say "most" because when I drained the old filter this spring, there was rust in it, and some had PASSED THROUGH the tempo brand filter I was using and had been collected and filtered out of the fuel supply by the on-board BRP fuel filters on at least one motor.).
The fact that some rust particulate is getting beyond the spin-on fuel filter is of some concern. These filters are supposed to collect very small particulates, and yet clearly, some very visible flecks of rust are getting past the filter to the engines. From what I can see, the larger flecks of metal and/or whatever else are still getting caught by the big cannister filter, but the OEM filters on the motors are also catching dregs.
I'm guessing that it may be because the filter was over full? I plan to change the filter every 50-75 hours moving forward instead of my once-annual habit (125-150 hours).
towboater posted 06-30-2008 04:30 PM ET (US)
Lookin fwd to part II Super Dave. Great trip..nice fish. I landed a 55" Sturgeon last Tues, the last hour of the last day of season.
My 18 Guardian work boat project is crawling along like a snail...(unhappy face).
Whether or not to install a below or above deck fuel tank has been a major issue I tossed around. Reserve fuel a big part of that.
I decided to go with two 20 gal above deck tanks to take advantage of the extra floatation AND visual fuel level.
Basically, Im in the process of boxing in the tanks and swivel seating above. Single 150 2 stroke for now, twin 70's when I can afford them. Below deck fuel tank is still an option.
QUESTION? (I am aware you are packing a lot of weight/HP)
Can you explain the handling differences at different fuel levels? i.e. What level of fuel (weight) do you prefer (incl the reserve tank) for best overall handling?
thx
mk
Buckda posted 06-30-2008 05:13 PM ET (US)
Small boat in big choppy lake = best overall handling when full fo fuel.
The 27 gallon Tempo tank ahead of the console is nice when the belly tank is empty, but the belly tank is hands down the best thing for helping smooth out the ride (except for the trim tabs - THOSE are priceless).
I find that I am happiest with the overall performance (minus top speed) when the above deck tank is removed from the boat completely and the belly tank is between full and 2/3 of full.
When loaded for camping like I was, there is a LOT of weight in the stern - two gear boxes in the splashwell at about 35-40 lbs each and two coolers ahead of the splashwell (128 qt and 72 qt Igloo's full of ice and food, my guess at 125 lbs at least for the big one, and 70 lbs for the smaller one) and a full 128 QT gear cooler under teh leaning post, and a camp stove back there, plus auxilliary anchor (10lbs) and dingy (75-80 lbs)....so under those conditions, having extra weight in the bow (27 gallon auxilliary tank, two 5 gallon jerry jugs of fuel drystuff food, drink cooler and personal gear and tackle boxes, plus anchor, chain, rode, spare anchor, campfire grate, etc in the forward anchor locker area along with tools and miscellaneous - it evens out for a pretty darn nice ride with only the occasional need for trim tab intervention into chop. I'm figuring 1,650 or so lbs, people, motors and gear...plus fuel (600 lbs or so)..so 2250 lbs if all of that is included, minus the arch, leaning post and the console. The recommended weight capacity is 1925 with a swaamped capacity of 3,000 lbs. I think we were definitely near the limits in terms of total boat capacity for sure.

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Author	Topic: 18' Outrage - "Usable" fuel in 63 gallon tank
Buckda	posted 06-26-2008 04:04 PM ET (US) In the past, there has been discussion on this site regarding exactly how many gallons of fuel are “usable” in a tank. A prudent skipper observes the rule of thirds – a third to get you out there, at third to get you home and a third of the tank in reserve; meaning it is difficult to really have an accurate idea of exactly what your boat’s range is on the main fuel tank. This past week, I had an excellent opportunity to determine exactly how many gallons of fuel from my 63 gallon capacity belly tank (1986 18’ Outrage) were “usable” to help me get to my destination. Equipped with a 27 gallon auxiliary tank in front of the console, I set off on a fishing/camping adventure in the wilderness of Lake Nipigon in Northern Ontario, Canada. Here is what I discovered: I pumped 228 liters (or 60 gallons) into the tank after running out of gas. Meaning there are about 60 “usable” gallons in the tank with 3 gallons remaining that cannot be efficiently used by the fuel pickup tube. I ran 40 miles at about 4 mpg after the gauge was fully rested on E. So when the needle was resting on “E” pretty solidly (i.e. not sloshing to E), there are about 13 gallons in the tank and about 10 gallons of usable fuel left, if you have the standard mechanical dial gauge. *NOTE – my gauge has been replaced with a newer one from e-components.net, but the only noticeable difference was that the new gauge uses a synthetic float and the original gauge used a cork float. This was mixed running, averaging 4 MPG (240 miles traveled on the GPS, divide by 60 gallons), including a fair amount of cruising at 2,800-3,200 RPM, some rough water operation and “trudging” and a considerable amount of idle/trolling, with a heavily loaded boat. Your mileage will vary depending on the motor and load. In my earlier calculations, I had been using an estimate of 58 usable gallons and 3.5 mpg economy to calculate my range for planning purposes. I think those are pretty fair and conservative numbers now. Moving forward, I will keep the 58 gallon figure but round up the economy to a “getting more accurate” 3.8 mpg to try to have less slush in the calculations. Incidentally, the penalty for running faster is severe. On the auxiliary tank, I ran 3,200 RPM for 40 miles and then 4,000 RPM for 46 additional miles and ran out of fuel at 86 miles and 25 gallons used, which dropped my economy to 3.4 MPG. Important to note in these days of expensive fuel prices.
tomol	posted 06-26-2008 06:33 PM ET (US) Good to know. I've always wondered how far I could go in "E". I knew it was a long way, but 40 miles... Now to the important stuff. Where are your story and pictures in the GAM?
Buckda	posted 06-26-2008 07:03 PM ET (US) Half of the trip is recounted in the Trips/Rendezvous section under Lake Nipigon. I also included a link to photos (Check out my 42 inch Northern Pike!). The other half of the story is still in development. I had to go back to work and haven't had a chance to finish it, but will soon. Dave
TransAm	posted 06-26-2008 07:47 PM ET (US) I need to go through that exercise, but my tank is 140 gallons. It would take me almost $700 to find out and I have no reserve tank but for a couple of 5 gallon red cans. My luck, I'd run out of gas in [a notoriously small town]. Maybe my next trip to Ocean City.
Tom W Clark	posted 06-26-2008 10:59 PM ET (US) I know the useable fuel capacity of the fuel tank in my Revenge 25, it is 140 gallons, the specified capacity of the tanks in the classic 25 foot models. I know this because I ran the boat dry one time when I first bought it. Interestingly, I noted that the placard on the Florida Marine Tank itself, located under the fuel gauge cover, says the tank capacity is 142 gallons.
alfred	posted 06-28-2008 06:48 AM ET (US) That is good info. I took it down to 10 gals once only, but normally fill when I am down to 20 gals.
Jerry Townsend	posted 06-28-2008 02:44 PM ET (US) Hey guys - careful. That is - the capacity of a tank is just the "nominal" capacity - the actual capacity may be more or less. Also - all fuel tank gauges were not created equal. All fuel gauges are not linear - some will fall off the "top-end" at a rate different from the bottom end. And remember - that gauge, even if accurate, is only giving the correct level when the boat is level - and not on plane or moving. I guess, what I am saying, is that running out of gas in the boat is not my idea of having fun - so make sure there is plenty on board. ------ Jerry/Idaho
Buckda	posted 06-30-2008 04:08 PM ET (US) Thanks for that Jerry - you're right. My post was simply to provide an example of approximation for other 18' Outrage owners so there could be some kind of comfort level with the fuel guage, which I almost always fill up once it get's near 1/3 tank, because I simply had never run it dry and didn't know. On a related note, I had replaced the fuel/water separating filter right before this trip with a new one, and last weekend, I dumped the contents of the new filter to determine if there was any water in the bottom of my tank, and to figure out if the dregs of the tank came up through the fuel pickup hose when the tank was run dry. As I've said, I have not ever drained the tank in this fashion in my ownership of the boat, and I really didn't know if I had water/ethanol problems in the tank, or what kind of debris is in there. I do know there are two bolts in the tank, because I've dropped them into the tank when installing the gauge. I also know there is a small screw in there, because I also dropped that into the filler tube when attempting to connect the chain on the filler cap. Anyway, here is what I found when I dumped the filter: No water in the fuel(this was not unexpected, I buy highway gas for the boat almost exclusively except for a few big trips each year). Also, there was a fair amount of rust. Since the tank is aluminum, I'm thinking that the bolts I dropped into the tank are disintegrating and resulting in some rust at the bottom of the tank. The filter is catching most of it (I say "most" because when I drained the old filter this spring, there was rust in it, and some had PASSED THROUGH the tempo brand filter I was using and had been collected and filtered out of the fuel supply by the on-board BRP fuel filters on at least one motor.). The fact that some rust particulate is getting beyond the spin-on fuel filter is of some concern. These filters are supposed to collect very small particulates, and yet clearly, some very visible flecks of rust are getting past the filter to the engines. From what I can see, the larger flecks of metal and/or whatever else are still getting caught by the big cannister filter, but the OEM filters on the motors are also catching dregs. I'm guessing that it may be because the filter was over full? I plan to change the filter every 50-75 hours moving forward instead of my once-annual habit (125-150 hours).
towboater	posted 06-30-2008 04:30 PM ET (US) Lookin fwd to part II Super Dave. Great trip..nice fish. I landed a 55" Sturgeon last Tues, the last hour of the last day of season. My 18 Guardian work boat project is crawling along like a snail...(unhappy face). Whether or not to install a below or above deck fuel tank has been a major issue I tossed around. Reserve fuel a big part of that. I decided to go with two 20 gal above deck tanks to take advantage of the extra floatation AND visual fuel level. Basically, Im in the process of boxing in the tanks and swivel seating above. Single 150 2 stroke for now, twin 70's when I can afford them. Below deck fuel tank is still an option. QUESTION? (I am aware you are packing a lot of weight/HP) Can you explain the handling differences at different fuel levels? i.e. What level of fuel (weight) do you prefer (incl the reserve tank) for best overall handling? thx mk
Buckda	posted 06-30-2008 05:13 PM ET (US) Small boat in big choppy lake = best overall handling when full fo fuel. The 27 gallon Tempo tank ahead of the console is nice when the belly tank is empty, but the belly tank is hands down the best thing for helping smooth out the ride (except for the trim tabs - THOSE are priceless). I find that I am happiest with the overall performance (minus top speed) when the above deck tank is removed from the boat completely and the belly tank is between full and 2/3 of full. When loaded for camping like I was, there is a LOT of weight in the stern - two gear boxes in the splashwell at about 35-40 lbs each and two coolers ahead of the splashwell (128 qt and 72 qt Igloo's full of ice and food, my guess at 125 lbs at least for the big one, and 70 lbs for the smaller one) and a full 128 QT gear cooler under teh leaning post, and a camp stove back there, plus auxilliary anchor (10lbs) and dingy (75-80 lbs)....so under those conditions, having extra weight in the bow (27 gallon auxilliary tank, two 5 gallon jerry jugs of fuel drystuff food, drink cooler and personal gear and tackle boxes, plus anchor, chain, rode, spare anchor, campfire grate, etc in the forward anchor locker area along with tools and miscellaneous - it evens out for a pretty darn nice ride with only the occasional need for trim tab intervention into chop. I'm figuring 1,650 or so lbs, people, motors and gear...plus fuel (600 lbs or so)..so 2250 lbs if all of that is included, minus the arch, leaning post and the console. The recommended weight capacity is 1925 with a swaamped capacity of 3,000 lbs. I think we were definitely near the limits in terms of total boat capacity for sure.