Fuel mileage efficiency

[Art]

Thanks TT. If you measure fuel before you start a trip and again when you stop you know without any monitoring systems how much was burned. Basic sight gauges are sufficient. Think most of us preplot or use the tract function of our charting systems so you know distance traveled. Will admit I do glance at my instantaneous readings but don’t think that changes my behavior. I’m more concerned by other factors. Things like timing to make use of favorable currents or achieving landfall at a desired time. So I’ll speed up beyond displacement speed to get my whole 6 h of favorable current or slow down to to arrive at a particular time or avoid a unfavorable current. Yes I know the “happy rpm” for my engine and now given fuel costs that’s my go to if other concerns aren’t operative. So my question is:

How does your monitoring system effect your behavior in running your boat?

Well put and questioned!

 

[rslifkin]

When I was delivering along the Pacific Coast, fuel/risk management was absolutely critical. That said, I would never rely on an owner's statement of fuel burn. They were always optimistic. I'd still be dead-in-water off the coast of Big Sur if I listened to owners.

But for the standard TF crowd who seems to mostly weekend dawdle, or do the Loop or the ICW, claiming risk-management is a wild exageration. Knowing fuel burn/capacity within +/- 20% or so is all about convenience, nerdish hobbyism, bragging rights, and economy. Sure it effects planning to know when you need to fuel-up. But way down the list is any safety-related concern.

Peter

Agreed. There are 2 big reasons to know your fuel burn very accurately. One is making a trip close to your range limits. The other is to try to burn as little as practical to keep costs down. When running against a current you can't avoid, for example, your speed over ground vs fuel burn (in gph) relationship changes, so without flow meters you're unlikely to find the most efficient speed against the current.

As far as being range limited, there are only a handful of places most of us here are likely to go that would test the range of even some of the boats on here. Without shipping my boat to the West Coast, I can only think of a few places I could go that might stretch my fuel range at trawler speed. And a good portion of the boats here have more fuel range than mine.

 

[Art]

Agree 1000%.

Having spent 2 careers that dealt with emergency or critical response in the air and on the water....

The ability to accurately determine endurance/range was crucial to good decisions/risk management.

True it isn't always about money, just sometimes convenience or even somewhat critical.

That's why when I took out the steel tanks with crap fuel gauges and put in poly tanks where I could always see fuel load and use accurate markings to accurately determine fuel burn under a variety of conditions.....it was one of my favorite modifications.

I can see where it's not necessarily important to some, as carrying large amounts of fuel and pretty consistent and predictable fuel burns bring less worry.....for me....it's just I'm my blood after all these years, plus to gain engine room space on my trawler, I dropped from 400 gallons to 112.

Good God man! That's a hella fuel capacity reduction. You have flex bladders available if needed for range? What kind of range was available with 112 gal tank [90 safe to use gals before refill]?

 

[psneeld]

Good God man! That's a hella fuel capacity reduction. You have flex bladders available if needed for range? What kind of range was available with 112 gal tank [90 safe to use gals before refill]?

300 mile range with reserve.

Southern NJ to Norfolk would be about the limit.

So other than a few legs on the loop that it wouldn't work for but easy to carry enough if needed, the rest of the East Coast was no problem for fuel...and probably not the Bahamas if careful planning used.

as a general comment not directed at Art......

To me it isn't a safety/risk management thing until it is.

The decision to go one way for fuel or continue to a safe harbor or critical medical assistance can be critical.

As they say in Washington, DC....knowledge is power and the military says "intel wins wars faster than guns". Knowing exact fuel state and burn rate can only make some decisions easier. They may be few, but they can often be the critical ones.

Look at my profile picture and tell me if you would feel comfy making a fuel decision you couldn't bet your life on?

 

[Art]

300 mile range with reserve.

Southern NJ to Norfolk would be about the limit.

So other than a few legs on the loop that it wouldn't work for but easy to carry enough if needed, the rest of the East Coast was no problem for fuel...and probably not the Bahamas if careful planning used.

as a general comment not directed at Art......

To me it isn't a safety/risk management thing until it is.

The decision to go one way for fuel or continue to a safe harbor or critical medical assistance can be critical.

As they say in Washington, DC....knowledge is power and the military says "intel wins wars faster than guns". Knowing exact fuel state and burn rate can only make some decisions easier. They may be few, but they can often be the critical ones.

Look at my profile picture and tell me if you would feel comfy making a fuel decision you couldn't bet your life on?

Just noticed your word "Sold" on avatar. Gonna buy another? If so... whatcha looking into?? - Best, Art

 

[psneeld]

Just noticed your word "Sold" on avatar. Gonna buy another? If so... whatcha looking into?? - Best, Art

Won't thread drift too much but my prediction of many years is coming true.... a man's last boat is a canoe on a nice lake.

Mine might be a canoe on a Ford Ranger towed behind my motorhome and then on many lakes.

Going 60mph to see family friends all over the country is working better than 6 knots.

Better fuel efficiency with the motorhome and the canoe...win-win.

Plus.... I have plenty of waterborne friends if I want big boat traveling or marina life.

Hard to convince myself to going back.

 

[twistedtree]

How does your monitoring system effect your behavior in running your boat?

This is really what matters in the end, isn’t it.

I use it two ways.

First is to understand the behavior of the boat. Understanding the NMPG at various speeds factors into how fast I choose to run at any given time. It’s just one factor, with other as you describe like needing to be in a particular place at a particular time for currents etc, length of the cruise plan, etc. Also getting an understanding of weather impact on NMPG, again so I can decide how much I want to power through something versus plodding along. But as others have pointed out, once you know how the bot performs, it doesn’t change. I know people who figure it out, make a chart, and then just refer to the charts. It’s not something you need to monitor constantly other than perhaps to detect that you are dragging something or otherwise running abnormally.

Then the other use is on a long trip where range really matters. A crossing would be the obvious example, but even a long coastal cruise is can matter. We arrived in Prince William Sound with limited fuel, and there are only three places in the whole sound with fuel. Having the range to get to one location, and still have a backup plan required close attention. To me this is all about monitoring ACTUAL NMPG as you operate so that you are adjusting speed in response to weather and currents to maintain a desired NMPG. I think this is where live data is valuable, but acknowledge it not a really common situation.

And just to draw in some other perspective, consider your engine temp gauge. It never changes under normal condition, yet we all have one, front and center. Why is that more important than a live NMPG gauge? I’d argue that the NMPG gauge is much more import since it is responsive to how you operate and your surrounding condition. Just food for thought, since habit is always a factor. Monitoring gph is another example. I’d argue that it’s not a useful thing to monitor without completing the calculation to get NMPG. But we monitor it because that’s what’s been traditionally available.

 

[Hippocampus]

Excellent post TT and agree with much you say. I do glance at my monitor time to time for just the reasons you describe. Especially to have a sense of the entire propulsion system. I do make use of the countercurrent along the US east coast and often temperature isn’t sufficient especially with breakouts and curls but a change in VMG at a constant rpm is the common clue. Rather than doing that calculation a glance at speed when I’ve been doing a constant rpm is without even looking at fuel burn is almost always what alerts you. Same with general health of propulsion. If I’m going slower without my having changed throttle something is up. Don’t need a flow gauge to know that. What that is is limited. I’m fighting current, sea state has changed and I’m spending energy going up/down and through waves, I’m dragging something or have fouled the screw, something is wrong mechanically. For all of these there is very rarely the need to look at fuel burn to be aware of troubles. Totally agree it’s very much worthwhile to have a chart
Speed (Knots)
Engine RPM
Coolant Temp 0F
Load
Throttle Position
Oil Press
Turbo Boost
Fuel (GPH) Consumption
Voltage
And do set times in all compass cardinal points at common sea states and wind speeds. (Don’t have real bumpy yet)
Agree doing such a chart periodically is also worthwhile. I further think it’s worthwhile while at anchor (or in slip) to figure out your usage for the most recent transit and chart it. That graph is informative and useful. But for most folks they can get the information other ways than a flow monitor. Am I pleased I have monitoring. Yes. Is it something necessary. Probably not. Is it something I compulsively monitor. No. Does it get a glance when I sense something may be off. Yes. But if I can’t immediately explain what’s off I’m going to go through the same diagnostic behaviors fuel flow gauge or not.

Also have tank gauges. Even having those at the helm is a luxury and not key. On any modest transit one of us goes into the ER time to time. If the trip is long enough for watches it’s de rigor at watch changes at a minimum . At that time do look the sight tubes and record what they say. Again a few seconds on the IPad you have a reasonable high/low for residual range. But as Peter mentioned and you accept for most of us it’s a rare time we’re past a 20% reserve. More common concern is price and ease getting in and out of the place. You are an outlier as I was. Very few people on sail or power voyage. I deeply miss it and believe it’s unfortunate most of us don’t use our boats to their capabilities. But there’s great joy with more limited usage. Think much of this is like people buying balls to wall rock crawling trucks and Jeeps to use as commuter daily driver.

 

[smitty477]

Agreed. There are 2 big reasons to know your fuel burn very accurately. One is making a trip close to your range limits. The other is to try to burn as little as practical to keep costs down. When running against a current you can't avoid, for example, your speed over ground vs fuel burn (in gph) relationship changes, so without flow meters you're unlikely to find the most efficient speed against the current.

As far as being range limited, there are only a handful of places most of us here are likely to go that would test the range of even some of the boats on here. Without shipping my boat to the West Coast, I can only think of a few places I could go that might stretch my fuel range at trawler speed. And a good portion of the boats here have more fuel range than mine.

"Agreed. There are 2 big reasons to know your fuel burn very accurately. One is making a trip close to your range limits. The other is to try to burn as little as practical to keep costs down"
Fuel use can also be used for these...
- condition of boat bottom
- syncing issues with twins
- health of engine(s)
- conditions of running gear/props

 

[Hippocampus]

I seem to want to check my zincs, running gear, see what that bump in the night did and bottom periodically. I like to look at it so do so. Don’t think monitoring changes that. Would do it anyway. Don’t know how monitoring tells me about zincs, cutlass bearing play or dings through the paint. I’m a delicate flower. Whenever I’m anchored in shallow water where the water is warm (I’m in New England) out comes the flippers and mask for a look see. Maybe old school but seems to work pretty good. On occasion you pick up a loose nut holding a zinc before it’s lost or a problem with a thruster blade or such. Monitoring just doesn’t replace a look see imho. When we were in tropical waters would snorkel off the boat. Every time took a look see first or last. Now in cold waters more of an issue but think it still needs to be done. Wonder how often monitoring is the impetus for engine or trannie work? Would think you know your boat and would know something is off. So yes if you’re working at the limits of range like TT understand the concern. Beyond that do wonder. Nice feature yes. Key need I don’t know.

 

[smitty477]

I seem to want to check my zincs, running gear, see what that bump in the night did and bottom periodically. I like to look at it so do so. Don’t think monitoring changes that. Would do it anyway. Don’t know how monitoring tells me about zincs, cutlass bearing play or dings through the paint. I’m a delicate flower. Whenever I’m anchored in shallow water where the water is warm (I’m in New England) out comes the flippers and mask for a look see. Maybe old school but seems to work pretty good. On occasion you pick up a loose nut holding a zinc before it’s lost or a problem with a thruster blade or such. Monitoring just doesn’t replace a look see imho. When we were in tropical waters would snorkel off the boat. Every time took a look see first or last. Now in cold waters more of an issue but think it still needs to be done. Wonder how often monitoring is the impetus for engine or trannie work? Would think you know your boat and would know something is off. So yes if you’re working at the limits of range like TT understand the concern. Beyond that do wonder. Nice feature yes. Key need I don’t know.

On a single engine trawler operated at below hull speed I would guess there is less of an advantage.
On a boat with twins it has been an immediate help in diagnosing a failed flex turbo hose, a wrapped prop, and some substantial barnacles mostly on one side. It has helped find a damaged prop on couple of boats and on a RIB with twins rather quickly - always a help to sync engines and baseline performance.
We also dive on our own boat in Long Island sound and I must say in the months before June and after Sept it pretty darn cold down there.

 

[Art]

Having docked/used our Tolly in SF Delta's freshwater [warm 5 to 6 months a year] for 13 yrs I often masked and flippered under the boat. Kept her bottom in good shape as well as anodes serviced and cooling-water intakes clear of debris.

Now that she'd docked in SF Bay's colder saltwater I'll hire out bottom service.

Had her bottom painted, underwater equipment serviced, and new boot stripe applied last September, 2021.