2011 df150 burning too much gas help

[akcruzer]

motor idles and runs normal, but burning way too much fuel I tried adding seafoam since this is the first time I am running the motor. tried fresh gas,

[Moonlighter]

More information required!

Exactly how much fuel does it use now? Mpg? L/hr at x speeds?

What boat is it on? Length, weight etc?

What rpm can you do at full throttle, trimmed out, with a normal load?

[akcruzer]

2011 df 150

its a 27ft aluminum boat running a 19 pitch prop burning about 8miles 4 gallons of gas. I had a Honda 130 forstroke on it before nowhere that much fuel burned. just to give you an idea.

[akcruzer]

I had no rpm guage mounted a Honda rpm guage but ran it with guage and without, trimming out doesn,t help. all of this is with no lload. if the guage is right it will bury the guage reading at 8000 rpms. I realize that the guage is a different brand but did try with and without the guage no other gauges yet. this is the first time I am running the motor bought over the winter was told it was fine. I have worked on 2 strokes over the years, so I have some experience. I have never worked on fourstrokes not sure where the fuel pump would be,

[akcruzer]

2011 df 150

wide open will show 38mph

[Harper]

In the first place, your Honda gauge is NOT working properly with your Suzuki. There is no way that you are turning 8000 RPM. Since I don't know what you mean by a "gauge" (just a tachometer, or some sort of combination readout?), I also question where you're getting your information that you are burning 4 gallons of gas in 8 miles. In fact, I have VERY serious doubts about THAT assessment also. The motor would not be running good at all pouring that much fuel through it.

You need to rethink your whole problem, IF (and that's a big IF) there is indeed a problem.

[artdf175]

I agree with Harper
Your tach or whatever you are measuring RPM with is not configured properly
6,000 is pretty much max
Just how are you calculating fuel burn?
Seems fuel flow meters measure g/hr
But please tell us more with details about equipment guages type of GPS /depth finder and how you estimate fuel consumption
Art

[akcruzer]

2011 df 150

I don,t know if the tach is reading correctly. it just a tach. showed idling at 900 rpms. that's why I ran without it at first. I got a five gallon gas container put 4 gallons roughly 20min travel time distance about 10miles. round trip I used a gps to measure speed. I will zero out gps to show correct distance. The motor normal from idle to wot. the boat is 27ft . I had a Honda 130 onthis boat last year. I am just using this as a reference. I know it might burn more but I know the Suzuki wouldn,t be much more.

[artdf175]

your Tach probably has a slider type switch on the back
normal idle is probably closer to 600 RPM
so lets understand the math
if you used all 4 gals in 20 minutes 12 gal per hour
went 10 miles with that = 30 MPH
or a burn rate of 2.5 miles per gallon
--
the other math 38 MPH /3 12.6 miles/ 4 = 3.1 miles per gallon
a 25% difference

doesn't take much difference to change the math

your GPS.. are you using a NEMA 2000 backbone to tie in the depth and GPS function?
IF you are.. it would be easy to connect in an engine interface cable thus letting engine can provide all the figures for you to read out on the chart plotter..
i.e. reason for asking the questions about the equipment you are using
better input of information gets better answers back to your question.
Art.

[2014DF25ARS]

I've heard an old rule of thumb: that an outboard motor at WOT will burn about a gal/hr for each 10 HP. So a 150 HP motor will burn around 15 gal/hr at WOT.

That's an old rule, based I'm sure on experience with 2-stroke outboards. I don't know if it's supposed to apply to 4-stroke engines. But I DO know that I have a Suzuki DF25A on my small (13 ft), light (250 lb) aluminum boat, and at WOT (30 MPH) the SMIS gauge tells me I'm burning 2.4 gals/hr and getting about 11-12 MPG. When I back off to about 4500-5,000 RPM (23-24 MPH), my burn goes to around 1.3 gal/hr and 16-17 MPG.

Bottom line to me is that the old gal/hr/10HP rule still seems to be in the ballpark at WOT for my fancy new 4-stroke. And if that's correct, then your 150 HP motor should burn around 15 gals/hr at WOT, and probably considerably less with better MPG at less throttle.

Perhaps you were running the Honda at lower speeds? Or maybe you're under-propped with the Zuke?

[akcruzer]

2011 df 150

I just got off the water. ran steady 26mph,12 minutes went through two gallons gas. running about half throttle. I am sure when I run at the reduced speed that I should get way better range. give you an reference I fished with this boat buying ten gallons at a time. easily I would run for the day commercial fishing. I will get a manual half to order it. no dealers within 500 miles.

[Harper]

All right....so you're burning 10 GPH at that speed, getting 2.6 MPG. Pull your spark plugs....all of them. Take a picture and post it if you can. You might have a leaking injector on one cylinder. Also make sure you have no external leaks. It's not bad enough to make it run terrible, but you should get a little better economy than what you've indicated. Of course there are many, many variables that come into play, and your run might not be indicative of a problem at all. Under different conditions, it might do better. A true reading of how it will perform has to be averaged over a number of outings.

[Moonlighter]

There are still too many unknowns to help you much.

While you've told us it is a 27ft aluminium boat, we dont know what style, weight etc. Some photos would grealy help.

Also, without a tacho, you have very little idea of what revs you are running at and therefore whether you are way overpropped or not. If you are not hitting the rev limiter (engine will miss and carry on if you are) at full throttle, every chance that you are overpropped significantly. Which will send your mileage out the window.

Add to that that you really dont know the condition of this used engine .... Have any basic tests such as compression, leakdown been done? Did you get a printout from the ecu before purchase?

Anyway, for what it is worth, the link below is to a Suzuki performance test of a 150 on a 21ft fibreglass boat. You will see that max fuel flow reached 16.3gph but it was still achieving 2.97 mpg at those speeds, and at 6150rpm. The same boat was achieving 23mph using 4.3gph at 3500rpm, which works out to 5.4mpg.

http://www.suzukimarine.com/product%...20Open%20DF150

Against that, your results look pretty bad, but then again, we dont know your boat, how heavy it is or how easy it is to push. That said, you say that a 130 Honda pushed it OK and used less fuel.... The Zuke should be far better than the old Honda and at least as economical.

So something is not right.

What - who knows?!

You need data! To quote W Edwards Deming: "Without data, you are just another person with an opinion"

These modern engines can seem to be running OK when in fact they are not.

I think you need to get back to the basics, check compression etc, fit a proper Suzuki tacho (preferably the version with the 3 warning lights on the lower section) so you actually know what rpm you are doing. The warning lights flash code sequences to tell you about problems too, as well as the oil change reminder function.

Depending on what that turns up, then get someone with the Suzuki diagnostic software (SDS) on a laptop to hook it up and run thru standard test regime and see what they find.

Otherwise we are all just guessing.

[tsturm]

I just got off the water. ran steady 26mph,12 minutes went through two gallons gas. running about half throttle. I am sure when I run at the reduced speed that I should get way better range. give you an reference I fished with this boat buying ten gallons at a time. easily I would run for the day commercial fishing. I will get a manual half to order it. no dealers within 500 miles.

Order the suzi digital tach. It will tell you fuel flow, real RPM
& be done with it.
I have a DF175 (2013) & push about 4,000 lbs, 25' glass, W/17p prop.
10gph = 20kts, 17gph = 29kts etc.

[akcruzer]

2011 df 150

here is an update. blew out the injectors, reset by turning key off and on one of my friends told me to try that. ran 4 gallons gas, 26mph ran for 32min. so I doubled what I was getting before. I do plan on getting the Suzuki gauges, just out of my budget right now. right now it has doubled the mileage. will check plugs. thx for the input. from everyone.