DF 115 missing at low rpms.

[Atipop]

Hi Everyone! My 2006 DF 115 is missing out at lower rpms. After reaching ca. 2000 rpms it takes the revs and has power, not quite hitting the top rpms as it should but still runs at 32 kn instead of 37.

Changed the brand new spark plugs to other brand new ones,
Cylinder 1: lightly white, all good actually
Cylinder 2: perfect
Cylinder 3: just like 1
Cylinder 4: a bit black

all this after running them for approx. 2 hours...

The boat is impossible to maneuver at lower revs

So far: changed the fuel line, the hand pump, emptied the btw. clean water separator filter, tried removing all air from the fuel system, looked in the air filter house (clean) checked the throttle body (clean), ignition coils seem OK.

I found in other forums that many of you had the same issue with other DF-s 90, 100, 115, 140 etc. Did anyone solve it? Thermostat? Water pressure valve? Unclean injectors? Check engine is not showing anything...

[catacom225]

Hi, I had a similar situation with my 140, pulled the leads off one by one while running and found No 4 had no responce, checked spark and there was. Next thing to check was fuel, removed the connecter from No 4 and found some green corrosine, cleaned it all up and it perred like a kitten

[Atipop]

Was the green corrosion on the electrical connection of the injector? Or on the end of the injector itself?

[redlowrey]

Run the engine on the muffs and bring the revs up to 1500rpm on the warm up leaver, remove each spark plug lead one at a time and see if you can pick which cyl is not working. If the miss is located to one cyl, when you remove the lead there will be no change in rpm.

If you can do a compression test when the engine is cold would be handy and make sure you open the throttle when cranking. I like when you say the ignition coils seem ok, what's that supposed to mean.

After you have run the engine at 1500rpm for fifteen minutes, stop and remove the plugs and note the colour of the porcelain on each one and see if number 4 is wet which I think is the clue to your problem.

[catacom225]

It was on the injector, and plug was slightly wet

[Atipop]

I'll look into it thanks

[Atipop]

It was the injectors

Hi everyone and thanks a lot for replying.

My injectors were extremely clogged up. 3 out of four were barely spraying anything. 3 cycles in the ultrasound cleaner worked a miracle.

Tested all four before cleaning and during the flow trhough test they produced 12, 15, 21 and 87 units. Test after the third cleaning cycle: 87, 87, 86, 87.

Put them back in, now I have a boat that flies above water, revs to 6000 with ease, 42 knots, got a steady idle and ability to maneuver the boat at low speeds again.

Feel relieved although the questions remains... how does all that dirt (you can see it in the injector rail, looks just like dirt from the gound) pass two fuel filters!?

[Atipop]

I like when you say the ignition coils seem ok, what's that supposed to mean.

the coils and the ECU seemed OK, because after I talked to the Suzuki repair guy, he said that if these would be the problem I'd have a check engine code. Plus I've tested the spark plugs and they all were sparking as they should.

As it turned out I had the number of the cylinders the other way around. So Nr. 1. was slightly black the rest were grey-white(ish). Meaning those three cylinders had little to now fuel at all.