2009 DF115 Not getting full throttle sometimes..

[Moonlighter]

This is one of those annoying, occasional issues that seem to be hard to pin down, so here's my attempt to describe what has happened and the circumstances in the hope that someone here will be able to offer some advice on how to resolve the issue. It doesnt happen every time - just every third or 4th trip.

• Drive out to fishing grounds about 45 mins run, and drift around, at end of each drift, start motor and move back to the top of the drift - most times, not going fast enough to plane, just a fast idle speed back to top of the drift. Turn off and drift for maybe 10 mins, then repeat.
• Did about a dozen drifts as per above, and then decided to move to another spot some distance away. Start motor and attempt to accelerate up onto the plane.
• Motor starts and seems normal, but when push throttle forward it's like the throttle is only partially opening because you don’t get full power - barely enough to gradually get onto the plane, but only just, despite pushing the throttle fullly forward. Motor sounds normal in that its not missing, running rough or anything, but it just doesn't have any real grunt. It will idle along happily. As I say, its like somehow you're only getting 20% actual throttle, despite pushing the throttle level down hard.
• So throttle back to idle, turn the engine off, pump the fuel bulb up hard (it was a bit soft), re-start motor, and its instantly back to full normal performance. Runs fine, doesn’t miss a beat, accelerates hard like it should.
• Did a few drifts, then head home, engine runs perfectly. Actually stopped 2/3 of the way home and idled around watching a tiger shark lunching on a dead dugong for 10 mins, then blasted off back to the ramp, still running perfectly.

More annoying than anything, but still a bit concerning that it might happen one day in a position where you need it to respond and when it doesn't…..

Anyway hopefully this explaination helps, would be good to get a solution that stops it happening.

The only other thing to add is that the days it has happened have been quite warm, but last time it was overcast with minimal sun, but quite warm (28C) and humid. Not sure if that's relevant or not.

Has anyone come across this sort of problem before?

Cheers

ML

[JUST-IN-TIME]

you have fuel restriction on the motor

[Moonlighter]

Thanks - but can you be more specific? I have of course checked all fuel hoses for kinks, blockages or similar and cant find anything obvious there.

The motor is only 6 months old and has done around 50 hours.

Many thanks

ML

[JUST-IN-TIME]

run it off a aux gas tank

[nelbur]

It sounds to me like you are getting some vapor lock while the engine is setting while hot, and it is not able to expel it fast enough when you accelerate. The next time it seems to be bogging down idle back and pump the bulb up without turning the engine off. Once the bulb is pumped up, see if it will plane out normally. This vapor lock problem is fairly common on four stroke Suzukis judging from the forums, and my experience with my DF 140.

[Moonlighter]

Thanks for that - yes, a vapour lock or something like that is what I was thinking, maybe fuel backflow. I am going to go over all fuel line joins this weekend and chack and tighten everything, and double-check for kinks etc.

The weird thing is that it only does it occasionally. If it was regular then the vapour lock would make more sense. My Suzuki tech is doing some research on this for me too.

I did see that on some other sites people had put restrictors on the fuel lines that prevented fuel flowing back down the fuel lines. Maybe the valve in the fuel bulb is not working properly - I do have a spare Yamaha fuel bulb in as new condition, so might change that as well and see if I can eliminate the problem thru a process of elimination.

Cheers

ML

[nelbur]

All gas outboards are supposed to have an anti-siphon valve on the fuel tank dip tube. This is a check valve which, if it is working properly, will not allow fuel to flow back into the tank. The check valves in your bulb are typically junk and can not be relied on. The anti-siphon valve looks like a barbed fitting with a longer hex section. You might want to remove the hose from the valve and using another hose, be sure you can not blow back toward the tank. If you can, the valve should be removed and cleaned out.

[Moonlighter]

Thanks for that information - but here in Australia those anti-syphon valves are, as far as I can ascertain, not required, very few people have heard of them, and very few boats would have them fitted.

Having said that, I think it is possible that this could be at least part of the problem. So I have done a internet search and found the scepter/moller part numbers for the alloy version of this valve and I called my local marine chandlery, they will see if they can get one for me.

From what I can see they have a standard 1/4 NPTF thread, which will screw directly into the outlet port on my water separating fuel filter, so that will stop backflow of fuel from the outboard as far as I can tell? I cant screw it directly into the tank because it will not accept that kind of fitting.

Thanks again for your thoughts, will give those things a try and see if it sorts the problem out.

Cheers

ML

[JUST-IN-TIME]

run it off an aux gas tank like a said

your going to start to pull hairs out

if it run perfect, then bad gas tank or fuel lines

[Moonlighter]

Hi Just in time

I appreciate the suggestion, however as I said at the start it is a problem that doesnt happen every time I take the boat out - only happens occasionally. So running it off a portable tank really isn't going to help too much as far as I can see, unless I run it for several trips off a portable, which really isn't practical to do.

Also, the boat is only 6 months old, so has a new fuel in-built tank, new fuel hoses, and to be sure I've checked them right from the tank thru to the motor, and they are fine, as you'd expect on a new boat.

I also know of 2 other DF100/115's that are doing much the same thing.

I found a clip on the fuel/vapour return hose at the top of the engine that was kinked a bit where it was held by a retaining clip, so have removed the clip and squeezed the hose back into shape. Also have tightened all the hose clamps on the fuel and breather lines, and replaced the fuel filter element. Will see if that sorts the problem or not and will post here if it looks to have been successful.

Cheers

ML

[nelbur]

If it is a vapor problem, Suzuki is very familiar with it. They have successfully treated the problem for some who are under warranty by installing an electric low pressure fuel pump in line, probably located on the boat, to help the low pressure pump get rid of the vapor. The problem is typically intermittent, possibly depending on how much heat soak there is from the way you were running before you shut down. Their solution points to a low pressure pump poorly designed to expel the volume of vapor sometimes produced. If you install an anti-siphon valve, the next step would likely be a new low pressure pump, but I have chosen to just live with the problem since it is so intermittent.

[borryking]

I have exactly the same problem on my 2009 DF100 with less than 40hrs on the clock:

http://www.suzukioutboardforum.com/s...t-rev-out.html

Since my last post I have rerouted the engine fuel hose to eliminate the sharp bend, changed spark plugs, checked fuel tank breather hose for kinks, checked water separator for water, and

Another possibly irrelevant point is that both Moonlighter and myself have NMEA networks set up through the engine diagnostic connector (in parallel with existing gauges). Not sure if it is possible that this might be having an effect. Is it possible that because we have gone in through the diagnostic terminal that the motor is going into diagnostic mode?

To add to the possible vapour lock issue discussed above: I took my boat out two days ago in cool conditions (both ambient air and water) and after the motor had been warmed up idling for 10 minutes it did it as soon as I tried to jump on the plane from the boat harbour. Retried with very gradual throttle opening and no difference. Shut down and restart also had no influence. It wasn't until I shut down tilted the motor right up then down and restarted that the problem went away. The motor also cut out a couple of times on the plane doing 15-20kts (didn't stall, just lost power). I haven't tried pumping the bulb.

I will try a tote tank next week and see if that changes anything. Mine seems to do it more often than Moonlighters.

[Moonlighter]

Bringing this one to the top again because, at last, we seem to have a solution!

Got a call late this week from a Suzuki tech guy who has been investigating this issue.

They have diagnosed and found a solution for the issue where sometimes the engine will start but not want to accelerate beyond about 3000rpm.

Firstly, they found that this only happens on engines that have the NMEA2000 engine interface connected. Disconnect interface, the problem disappears!

In laymans terms, we now know that the engine interface gets powered by the connection to the ECU, which of course is via the adapter cable that we connect to the SDS port on the engine. It is not, as we earlier assumed, powered by the network.

On some boats, for some unclear reason, when cranking, the voltage that is getting supplied to the interface via the SDS port sometimes drops sharply below a critical level, and this causes a low voltage signal to go back to the ECU from the interface, causing this problem - the ECU interprets this as a sensor warning and puts the engine into a "safe mode" that wont allow it to accelerate above 4000rpm and simultaneously sets spark advance at zero.

I have seen the diagnostic data they have, and it shows what is happening quite clearly.

This explains and is consistent with the symptoms of doughy acceleration and unwillingness to rev to full speed that we had experienced.

The solution they have developed and that testing on a number of affected boats shows to have worked, is to run 12v power direct to the red wire in the interface cable. So in other words, disconnect the power wire supplying 12V to the interface that comes from the SDS port, and run a separate wire from 12V+ to connect to the red wire in the interface cable.

Suzuki Australia have now issued a Service bulletin to Australian dealers about this issue. US dealers might be able to get a copy from them if you ask, but they wont release the bulletin to the general public/owners, it is for dealers only.

On my boat, I have done this modification this morning and will be taking the boat for a test run (code for fishing trip!) tomorrow morning. I connected the new red wire to the positive busbar behind the dash. So it will get power from the house battery, thus totally removing any chance of voltage spikes when the engine is started - i have a BEP dual battery system with vsr so they are isolate from each other.

I will let you know how I go. But I am confident we finally have it nailed!

[redlowrey]

Good stuff moonlighter, I think your right on the money.

[Moonlighter]

The test run went well today on 2 counts.

First, the engine ran perfectly. I intentionally stopped and started it several more times than necessary and every time, it accelerated onto the plane perfectly.

I even tried to provoke a problem by starting the engine without waiting for the beep to finish when the key is turned on. In the past this was a surefire way to cause problems. But still, it started, ran and accelerated perfectly.

So the solution developed by Suzuki here in Australia seems to be working.

Secondly, we caught 28 really nice crabs in our 8 pots, only lifted them twice, and was only on the water at 7am. So, had crab sandwiches for lunch and toasted crab jaffles for dinner. Yum!