Some real world GPH numbers from a gas powered '97 400DA

Stee6043

Stee6043

Well-Known Member
Jun 1, 2015
6,733
West Michigan
Boat Info
1997 Sundancer 400
Engines
7.4L Gassers
I finally recovered my receipts from a July trip across Lake Michigan. Just before the 4th of July I took delivery of my new-to-me 97 400. I was quite curious what kind of mileage I'd get with this boat...though I misplaced my receipts until this past weekend :)

My first leg on full tanks was Sturgeon Bay, WI to Pentwater, MI via Ludington (this is where I turned South-ish to fuel in Pentwater). Total miles (nautical) on-plane was 72. Total fuel burn was 117 gallons. Total time was a tick longer than 3 hours running 23-24kts (SOG). Seas were 2-3 consistently.

The math puts me at .62nm/gallon. Right around 37/38 gallons per hour.

I was running the boat a little harder than I wanted to because we were coming off 3 days of small-craft conditions (5'-6'+) with a forecast for building waves and small craft conditions again that afternoon. I ran 3,600RPM just about the whole way. I would have preferred 3,200-3,300. Due to the chop I was also full-tab 100% of this ride.

My gut tells me this is a pretty good result for a bumpy ride, full tab, a bit more RPM than ideal. I feel like I could have driven those GPH numbers down into the mid/low 30's had I been cruising 3,200 with no tab, calm seas. Perhaps next year I'll have to find out...

Of course had I bought diesels it would have been Prius levels of economy, no tab required due to added weight, drink a beer while underway due to stability, and I'd probably have been able to skip that stop in Pentwater :)
 
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I like the way you take the words out of all the diesel owner’s mouths. Well done. Enjoy!
 
I almost never cruise with 0-tab. In fact, most of my cruising is way slow with tabs digging in as far as they can.

I also calculate in sMPG. .71 sounds better. :D

If you're going to cruise in that boat, consider installing meters. You should be able to tune your cruise to squeeze a few more hundredths out in decent conditions. They can also better calculate range, allowing you to travel lighter, stop less etc. I've had my meters for 9 seasons now. Wish I had them from the get-go.
 
My last 2 fill ups I averaged .749 and .758 mpg. I mostly run around 3400 rpm, 24 mph and not much tabs at all. Fuel meters are my next upgrade. I am curious to see what my average is going to be for the whole year. AHHH who am I kidding, no I'm not.:D
 
Ezsteps said:
My last 2 fill ups I averaged .749 and .758 mpg. I mostly run around 3400 rpm, 24 mph and not much tabs at all. Fuel meters are my next upgrade. I am curious to see what my average is going to be for the whole year. AHHH who am I kidding, no I'm not.:D
Click to expand...

Is that nautical miles or statute?
 
Ezsteps said:
My last 2 fill ups I averaged .749 and .758 mpg. I mostly run around 3400 rpm, 24 mph and not much tabs at all. Fuel meters are my next upgrade. I am curious to see what my average is going to be for the whole year. AHHH who am I kidding, no I'm not.:D
Click to expand...

You have a nice-running 400 though! Think about all the comments we’ve seen from people who assume we get .5 and even .4

I’ll be interested in your meter project. I’m having trouble with my GFS-10’s this season. If they’re wearing-out (which Garmin says is possible), then I might replace them with Fox gateways. I’d really like to be able to ignore my crazy tachs by reading digital info right from the ECM...
 
Nice boat, sound like an awesome trip!

I'm looking at digitizing the guages (Sea Ray tachs suck). Been looking at the Chetco G2 (http://www.digitalmarinegauges.com/products/sensor-interface-units/pro-sensor-interface-unit.html). Spoke to Joe (the owner) there this morning. A couple interesting things

1. This runs on a regulated 12VDC supply, so all of you guages will read accurately regardless of your alternator output
2. They are introducing fuel flow senders that should be $400/pair. Gas guys will be able to do twins for that, and Diesel guys for $800.

This seams to fix some of the shortcomings of the Noland RS11 as documented by Ttmott (http://clubsearay.com/index.php?threads/save-your-transmission-modifications.66004/) as well as adding transmission instruments and in my case EGT or boost (or both should I buck up for 1 per engine).
 
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Guys, I just saw this thread, I wired in Fox Marine interface boxes that pug into my gas MEFI 3 engine controllers and convert the engine signals into NMEA 2000 protocol that then interface with my Raymarine chart plotter. With this I get fuel flow in gals/hour, I ran a trial to see my fuel consumption which is below. It is in statute miles per hour. Note the scale is on the bottom is not linear.

upload_2018-11-11_7-38-3.png
 
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Wire-Setup_2.jpg


Here are the Fox Marine boxes and the wiring setup - all NMEA 2000 and interface to my Raymarine Screen
 
Raymarine-E90W-data_2.jpg


This was with the engine off but a sample of how you can configure the screen and the data you get. The beauty of this system is not cutting into your fuel system! You also get full digital RPM, coolant temperature, & alternator voltage
 
Last chart, you can really tell when she got on plane. This is for one engine.
upload_2018-11-11_7-31-35.png
 
Very cool Brian. As I was reading your first post I was thinking, "damn, I wish he had included a screen-shot..." Something about all that info is like data porn to me. :D

That's on a single display? Are you tempted to, and do you have space to add additional displays? I would find it difficult to switch away from all that data to see a boring chart. lol

So it looks like your best cruise is about 20.5 MPH returning what, about .72 sMPG? Did you tweak the tabs at each data point? I noticed in your graph a slight bump from the high teens to 20. That's interesting. I find the opposite - my best cruise is sub-20. In the low 3,000 RPM range I see a dip no matter how I trim her or what the load is, and then around 3,600 or so when I can lift the tabs I see econ climb a little. I should chart it out. Goal for next season.

On my last run this season, my GFS-10's decided to behave perfectly on an 11 mile run up to the island. Before I could get too happy on the way home, they started bouncing. :mad:

Aside from already having cut into the fuel lines, I keep hearing that flow meters are likely to be more accurate than injector pulse count from the ECM. Ideally, I'd like well-functioning meters combined with all the other data from gateways. I don't know how the system will handle duplicate fuel data though.

Have you had a chance to watch a couple of fuel fill-ups to gauge the accuracy of computer data?

btw, I posted/sent you that pic I had of your boat, right?
 
It's comforting to know that my old school math written on two fuel receipts can still keep up with all this new fancy technology!!! :)

That is a slick setup, Brian! Looks like a clean install.
 
I really want the Fox Maine connections, however, I have been cautioned they are not as accurate as the Garmin fuel flow meters.

MM
 
Guys, thanks for the good words! I actually think the Fox setup is pretty accurate, when I had my 330 Sundancer I installed Garmin fuel flow meters and they were a total pain to calibrate. It seemed like every time I would reset them I had to recalibrate them. I have not had a chance to go on a long cruise to compare the theoretical to the actual but so far based on the runs I have done I think they are not too far off. One good thing about the Fox set up is they are very repeatable!

On the run I did to do the graphs I didn't play too much with the tabs, that would be a good project for next spring. Also as you can imagine the numbers will be very different depending on how much fuel I have on board, 300 gallons = about 2400 lbs!

I do cruise at about 21 MPH, I have found that to be a good overall cruise point.

As far as the displays I really would like to run 2 additional Raymarine i70's, I have room on the dash but just haven't coughed up the additional $1000 to install them.

In addition to the screen display Fox Marine has an app you can run as the boxes have built in blue tooth.

Overall I have been very happy with the setup!
iPhone-bluetooth.jpg
 
Captain Brian said:
As far as the displays I really would like to run 2 additional Raymarine i70's, I have room on the dash but just haven't coughed up the additional $1000 to install them.
Click to expand...

Garmin does the same thing with their GMI instrument displays: the smallest screen they make, with the fewest functions, but yet they slap a huge price tag on it! I don't get it! :mad: I couldn't find any deals on the used market, so I ended up with a refurbed and a demo MFD for about the same cost.
 
RollerCoastr said:
Very cool Brian. As I was reading your first post I was thinking, "damn, I wish he had included a screen-shot..." Something about all that info is like data porn to me. :D

That's on a single display? Are you tempted to, and do you have space to add additional displays? I would find it difficult to switch away from all that data to see a boring chart. lol

So it looks like your best cruise is about 20.5 MPH returning what, about .72 sMPG? Did you tweak the tabs at each data point? I noticed in your graph a slight bump from the high teens to 20. That's interesting. I find the opposite - my best cruise is sub-20. In the low 3,000 RPM range I see a dip no matter how I trim her or what the load is, and then around 3,600 or so when I can lift the tabs I see econ climb a little. I should chart it out. Goal for next season.

On my last run this season, my GFS-10's decided to behave perfectly on an 11 mile run up to the island. Before I could get too happy on the way home, they started bouncing. :mad:

Aside from already having cut into the fuel lines, I keep hearing that flow meters are likely to be more accurate than injector pulse count from the ECM. Ideally, I'd like well-functioning meters combined with all the other data from gateways. I don't know how the system will handle duplicate fuel data though.

Have you had a chance to watch a couple of fuel fill-ups to gauge the accuracy of computer data?

btw, I posted/sent you that pic I had of your boat, right?
Click to expand...

RollerCoastr, where did you cut into the fuel line to install the meters? I installed Lowrance fuel flow meters on my 37 DA and it was very easy - I loved them. Not sure if I want to go this route or get the Fox units.
 
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