Fluctuating fuel consumption on 2014 DF300

[Fishfool]

I have twin 2014 DF300's that have been running great with great fuel economy.

I bought them brand new and they have about 200 hours on them.

Recently the starboard motor fuel economy/fuel consumption has started fluctuating when cruising in any type of sea condition. It can be flat calm or a little sporty and I get the same issue and only from the one motor. The motors will accelerate with no issue to all speeds and as soon as they get to whatever speed I choose the starboard motor fuel consumption will start to fluctuate up and down. For example at 4200 cruise in flat water the motor will go from the normal 2.2 down to .8 or 1.2 then back up to 3 and down to 1 back to 2 and so on. It jumps all around but the RPMS stay pretty steady maybe fluctuating by 50 and motor seems to run fine.

The motor has not thrown any codes, all the fuel filters are clean and water free, the primer bulbs are tight.

Does anyone have any ideas of what might be causing this issue?

[Moonlighter]

I would suspect an issue with the engine interface cable. They can cause these kind of problems at times.

First job is to check the software version of both engines interface cables. There is a newer version for 2014 engines that works better than the original V 3.5.0 that was used back then, if yours havent been updated we can give that a shot, its easy to upload.

Turn the key on to where it beeps.

Then, on any gauge, (I am assuming you have C-10’s?) go into the menu, select settings/network/devices then scroll down and select the Starboard engine from the list, and open it. It will show the software version there. Report back here with what it says. Check the Port engine and see if its the same version.

Also, just check that the Starboard engine harness connection under the cowl is plugged in firmly- the plug involved is the same SDS plug that is used by the mechanic to download data to the Suzuki SDS software. 4 pin plug. If its been serviced recently it might not have been plugged back in correctly. Make sure its firmly plugged in and no loose wires in the back of the plugs.

[Fishfool]

I actually have the old 4 inch SMIS gauges so I know I have the old software version of interface cables. The C-10's came out the year after I bought my 300's. I have actually bought a set of C-10's and interface cables that I need to install. That was going to be my next project after I sorted out the fuel fluctuation issue.

I guess it would be best to install the C-10's first since SW is upgradeable with them????

Do you have any pointers to installing the C-10"? I know I have to set them up but is it necessary to go through the whole programming procedure like the dealer did originally? Is it a plug and play and all I need to do is set up my pages.

I will get the SW version off the new interface

I really wish i could use the SMG4 gauge but I was told they would not work on my motors??????

What would be your advise with all this I am laying out there?

[Moonlighter]

I am curious why you bought new interface cables? (I hope you got new version 3.5.4 or 3.5.7 cables, the 2.9.4 wont work with your engines).

Your current setup will already have interface cables installed, and they SHOULD be the new software versions and they can be updated to current software simply by uploading the files via the new C-10’s.

Or, if you have a Simrad or Lowrance display already plugged into the network, they can do the interface software upload just as easily if not more easily than the C-10’s.

Anyway, if you remove the current interface cables and install the C-10’s, then yes, you will need to configure the interfaces, this is very easy to do using the C-10’s (or the Simrad or Lowrance displays as mentioned earlier). And if you are going that far with this upgrade project, I would also recommend installing a new network backbone using the multi-T’s. That way your setup will be 100% new, no old parts.

Then you can easily set up one C-10 to monitor the port engine and the other to monitor the starboard. The whole thing might take 15 minutes to do.

I can walk you thru it if you like. Piece of cake. (When you know how LoL!)

Also, do a google search for a Simrad IS-35 gauge user manual and save a copy. C-10 is a clone of that display and its 99% the same, just a few Suzuki specific tweaks. Well worth a read, it tells you in easy to follow instructions how to use them. They are miles easier than the cumbersome SMIS gauges and far more intuitive and flexible. The manual tells you how to set the gauges up so they show the data for the engine you want.

SMG4 oficially works with 2015 and newer. The MIGHT work with a 2014 DF300, maybe, but its an expensive exercise if they don’t.

But really, the C-10 setup should be just fine. Just don’t go bashing the buttons with ham fists all the time! Wipe them over with a damp cloth at the end of the day.

The keys to the system working reliably are:

1. matching the engine year to the interface software and then the C-10 software to the interface.
2. setting up the backbone correctly. Keeping it dry and cool.
3. good electrical supply to both the network backbone and to the engines themselves.

In my experience, at least 70% of the supposed “C-10 problems/failures” are actually engine or network power supply issues, backbone components failing or incompatible software. Another 15% are interface cables failing (sometimes due to voltage spikes) and its only the 5% remaining that are actually C-10 fails.

And if course we rarely hear from the 90% of users who NEVER have any problems with this system or the gauges.

[Fishfool]

Yes, I had to buy the 3.5.4.version because like you said the 2.9.4. version cables I had would not work with the C-10's. I use Garmin displays on the boat so I will do the upgrade once I have the C-10's installed. The biggest problem is now finding the time to get this all done.

I might need to take you up on the setup offer. I am generally pretty good at this stuff but you never know. I will reach back out once I get to this.

[Moonlighter]

The 2.9.4 cables could have V 3.5.4 uploaded to them, but as stated previously you need a C-10 or Simrad/Lowrance display to do that.

The interface version is tied to the engine year they are connected to, not to the gauges. If your existing cables are 2.9.4, they were always the wrong version for 2014 engines. Surprised they worked properly at all.

There is a sticky thread in the top section of this forum where I posted about setting up Suzuki NMEA2000 networks. The attachment to that thread explains it all including setting up and configuring the system.

[Fishfool]

I took the boat for a run today just to run it but also with the intention of checking the version. I had a strange issue today with the starboard motor having the fuel economy fluctuations. Today the RPMS fluctuated up and down by 200 to 300 rpm with the fuel flow fluctuations. No alarms or codes but I could feel the speed of the boat dancing in harmony with the RPM fluctuation.

No issue with idling in gear or running it up to 6K.

With the issue today I forgot to check the version, so I will go back to the boat tomorrow and get it.

Any thoughts on the big RPM swing?? 02 sensor?

[Fishfool]

I am new to this forum and still figuring out how to find things. Can you please give me a link to the thread about setting up NMEA2000 network? I can't find it and would like to read your suggestions. I have a pretty extensive network on my boat that has worked perfect since I did the hull up gut restoration in 2014........but I always look for more knowledge.

[Moonlighter]

https://www.suzukioutboardforum.com/...a2000-networks

There are a multitude of reasons why an engine might momentarily lose rpm…. Could be as simple as a bad spark plug, or a clogged fuel filter. Or stale fuel. Or something more complex….

Another important thing to note is that these engines are very voltage sensitive - if the ecu is not getting a good solid clean 12v then it can do strange things and loss of rpm is one of them.

This is often due to a corroded “white wire” this is the battery sub wire that provides power to the ecu. It is usually connected to the main battery switch or the start battery and there will be a fuse in it close to that connection. So this needs to be carefully inspected, cleaned, the wire and connections CAREFULLY checked for corrosion, repaired if necessary, and reattached and tightened. The fuse and fuse holder in that wire need to be inspected with similar attention to detail. As do the main battery cables. And the batteries checked and load tested.

[Fishfool]

I knew about the voltage sensitivity so, I started going over all the wiring today and so far it is spotless. All 4 batteries got replaced 6 months ago and are clean with tight cables. The plan is to work my way back to the motors checking all wires and connections.

I am still going to install the C-10's with new interface cables. Will I need to reset up all the vessel information such as the number of engines, number of fuel tanks and so on?

BTW......thanks for all your time and help!!!

[Moonlighter]

I knew about the voltage sensitivity so, I started going over all the wiring today and so far it is spotless. All 4 batteries got replaced 6 months ago and are clean with tight cables. The plan is to work my way back to the motors checking all wires and connections.

I am still going to install the C-10's with new interface cables. Will I need to reset up all the vessel information such as the number of engines, number of fuel tanks and so on?

BTW......thanks for all your time and help!!!

Yes, because all that info is held in the interface cables themselves. So its start from scratch.

Do it in the following sequence if you arent prompted when it starts up.

Turn it on when its all installed.

1. menu/System/fuel/vessel setup. Use the dropdowns to set the network to match your boat. Eg 2 engines/2 tanks. Set the tank capacity. Save and exit.

2. menu/system/network/devices, then select each Suzuki device in turn and select configure, set their locations according to their position using the dropdown menu. Don’t try to change the hp or year, they wont save anyway, so just set the locations as Port and starboard accordingly. The fuel level defaults to full, there is no way to change this. You should also be able to see the interfaces software version listed on that page.

Then refer to the IS35 manual, it tells you how to set each gauge so it shows data from the engine you want eg you can set the left side gauge to show data from the Port engine etc. The manual also tells you how to customise the info on each page if you wish to do that. All fairly straightforward. You will also find the refuel procedure is easier than the SMIS - go back into tjat fuel menu from step 1 and you will see the options there. You can reset trip, seasonal or simply fuel used.

[Fishfool]

Happy New Year!

Went to the boat again and I was wrong about the SW version being 2.9.4.
The SW version is way old currently being 2.7.

I also have a upper helm station with twin SMIS gauges and my guess is that when I replace the lower station gauges with the new interface cables and C-10's the SMIS's up top will stop working. Will it hurt to leave them in place hooked up or should I just unhook them from the network?

[Moonlighter]

Ok now we get more of the story.

2.7 cables are the “early model” cables that run a different software design. Those “luf” software interface cables are highly sought after because they can be used with engines from 2003-2008. You should be able to sell them easily.

Its very surprising to find them installed with 2014 model engines. I wonder why that was, perhaps the boat had earlier engines and they re-used the old interface cables with the 2014 engines. Or maybe whoever installed them simply didnt know how important it is to match the interface software with the engine year.

Anyway, the new 3.5.4 “swup software” version cables should work fine with those engines, and there is also a pretty good chance they will be OK with the upper helm SMIS gauges too. I would leave them connected and see how they go. We can later check the upper helm software version and possibly update it to one that works better with version 3.5.4 interfaces. You might have to set the SMIS gauges to look at the correct engine interfaces though, as they might not recognise the new interfaces.

One IMPORTANT thing to do to help in that regard is to reset network data sources once the new interfaces and C-10’s are installed and configured. After all that is complete, make sure that everything attached to the network is turned on. Engine keys turned on but they dont need to be started. Then, in one of the C-10 menus, go menu/system/Network/sources, then select the option in the top left to Auto Select. Follow the prompts and yes you do want to do this when it warns you that all data sources will be reset.

You need to get your head around the fact that the engines aren't connected to the displays in the same was as analogue gauges are. The engines are connected to the interface cables, and the interface cables send the info to the NETWORK, not to the gauges.

Any displays attached to the network can then receive and display the engine info.

The C10’s and SMIS are simply displays that are customised to show engine related information. You can have multiple displays all showing the same engine info. The gauge displays just need to be told which data from which engine interface they should show.

[Fishfool]

Just an FYI....giving you the history.

I purchased the engines, all cables, gauges and all rigging from Suzuki and rigged the boat myself. All the part numbers ordered came direct from a factory direct technician.

When I finished mounting the motors and rigging the boat the factory guy came to the boat to pair the controls to the motors and did all the programing.

As for the factory 2.7 interfaces let me know if you want them or know someone who needs them.....the least I can do for all your help.

[Moonlighter]

Ok thanks for that update.

Regrettably, not all dealers pay sufficient attention to the networking issues and/or they dont bother to read the technical bulletins or attend the training schools that Suzuki provides….. and thus we find situations like yours.

If you start a new thread here stating that you have 2 x 2.7 interface cables running .luf software, I am sure you will get offers for them. You will easily cover the cost of the new 3.5 version cables. Ive seen then go for double the cost!

Good luck with the upgrade project!