posted 12-14-2009 06:32 PM ET (US)        

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I have a 2006 mercury 150hp EFI 2 stroke which seems to be injecting too much fuel into the number 2 cylinder. The motor will run well with a new spark plug for a short while till it stops firing due to what seems to be too much fuel. Would a leaky fuel injector cause this problem? If so what would be the best way to clean them.

I have switched coils, plugs and leads over but still get the same problem on that cylinder.

Any advice would be great

Thanks in advance

posted 12-14-2009 10:12 PM ET (US)            

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Thanks Transam, I didnt realise it had seperate fuel pumps for each cylinder, I will check that out this afternoon.

I was also thinking if the "O" ring around that injector had failed it could cause a leak into that cylinder.

posted 12-14-2009 11:03 PM ET (US)            

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Until now I have never heard anyone mention that each cylinder on a Mercury 150-HP two-cycle engine has its own fuel pump. That seems very unusual.

In most fuel injection systems there is an electric fuel pump which creates a pressure in a fuel distribution system which carries the fuel to the fuel injector. I would like to hear more about the Mercury design with six individual fuel pumps for six cylinders.

posted 12-14-2009 11:06 PM ET (US)            

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Im assuming you are talking about the little square low pressure fuel pump. I would have thought all the injectors would have played up if that was faulty. All other cylinders are burning perfectly.

It would be good if that was the problem but the engine has only done 120hrs and is one year old, but I will check tonight.

posted 12-15-2009 06:55 AM ET (US)            

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OK...I took the boat down the boat ramp this afternoon, warmed the motor up and emptied 3/4 of a can of Powertune down the intake until it stalled. Left it for 10 minutes, restarted the motor and emptied the rest of the can in. I then drove the boat out the mariner with enough smoke to make the motor look like it was on fire. I then gradually built the RPM up and cruised on 3500rpm, then after 10 minutes sat on 5600rpm (WOT) for a few minutes.

Fuel ecoonmy went back up to normal, and the Mercury is now running perfectly on all cylinders.

What could it have been....maybe carbon caught in the reeds or on the tip of the injector? Seems to be all fine now though, even after 2hrs of driving at various speeds, idling and trolling around. Fingers crossed thats the end of that problem.

cheers

Jake

posted 12-15-2009 09:36 AM ET (US)            

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quote:

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"The mercury 2 cycle engine only has 2 fuel pumps Jim"

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I am glad to hear that, inasmuch as I was rather skeptical about the assertion that it has six fuel pumps. Having two fuel pumps, a fuel lift pump operated by crankcase vacuum pulses to bring fuel to the engine from the fuel tank, and a second electrically operated fuel pump to circulate the fuel at an elevated pressure among the fuel injectors was precisely how I thought a Mercury 150-HP V6 two-cycle EFI engine operated, and it is good to put to rest the notion that it had six fuel pumps, which, as I mentioned, I had never heard before.

posted 12-15-2009 10:09 AM ET (US)            

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quote:

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I am glad to hear that, inasmuch as I was rather skeptical about the assertion that it has six fuel pumps.

...and it is good to put to rest the notion that it had six fuel pumps, which, as I mentioned, I had never heard before.

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I too would be skeptical of an assertion that the Mercury V-6 may have 6 fuel pumps. I have re-read this article several times and see no assertion of 6 fuel pumps anywhere except in your citation. Thank you for appropriately putting to rest this confusing notion that Mercury V-6 outboard engines have a separate fuel pump for each cylinder. I do, however, see a suggestion that "You may want to check the fuel (lift) pump that feeds that cylinder." and then later amended "jake--Now that I think about it, I am not exactly sure if the mercury's have a separate pump to feed each set of cylinders." as other engine manufacturers do, and appended further to "I think Merc's may only have a single low pressure pump". In any event, I see no way to interpret any of this information as Mercury V-6 engines as having 6 separate fuel pumps, one for each cylinder.

posted 12-15-2009 05:17 PM ET (US)            

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I will take your advice and run quickleen from now on LHG.

The mechacnic told me to run Powertune through the motor before installing the new spark plugs. It must have dislodged some carbon and it got caught up somewhere it shouldnt have. I dont think Powertune can damage an EFI as the only sensor it would pass by is the MAP sensor.

Anyway I wont be using that stuff again.

Have a safe Christmas everyone.

Jake

posted 12-15-2009 06:23 PM ET (US)         

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Jake- Just curious - Now that you've had the 150 EFI for a while, how do you like it compared to the previous Optimax that you had? It is interesting that you went "backward" from modern DFI technology to what JimH likes to call "obsolete throwback" conventional 2-stroke EFI technology.

I, for one, still think the Mercury 2.5 liter EFI's are one of the finest outboards, per dollar of cost, ever built, at least until the Verado's came along. I really hate to see them go out of production.

posted 12-15-2009 06:55 PM ET (US)            

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I really like the Mercury EFI 150. It is definately smoother throughout the whole rev range than the Optimax was, and less rattles The EFI uses way less oil than the Otimax.

The Optimax was getting a fuel flow of 19 litres per hour at 3,500-RPM. The EFI does 21 litres per hour at the same RPM. This is our preferred cruise range as we travel 50-km to our fishing grounds. Converting back to km per litre the Optimax was 2.2-km per litre at 3,500-RPM and the EFI is 2-km per litre at 3,500-RPM.

The Optimax would get a lot better fuel economy at lower RPM but that does not concern me because we travel to our fishing ground and set anchour for the day/night we do not troll.

I am still comparing a 1999 Optimax to a 2006 EFI so I can't really comment on the same year motor. [For] service I prefer the EFI; it is a much simpler motor.So yes I am happy with the EFI and hope it gives me many years of service like [LHG's] have.

cheers,

posted 12-15-2009 09:19 PM ET (US)            

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How many cylinders are there in a set? If a set is one cylinder, there are six sets. In a two-cycle engine, the fuel induction system of each cylinder is isolated from other cylinders, so each cylinder is operated alone, or as a one-cylinder set.

Aside to LHG: Although I do not recall ever explicitly using the word "obsolete" in regard to these open-loop, non-programmable fuel injection engines like the Mercury V6 150-HP EFI, but in the year 2010 they _are_ obsolete, and soon the EPA will make that point for me. They were nice engines in their day, which was around 1990, although that same sort of technology was being used in cars in the 1970's. (The 1970's are 40-years in the rear view mirror.)

posted 12-15-2009 10:34 PM ET (US)            

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There are 3 sets of cylinders in a mercury V-6 outboard engine; I thought this was made perfectly clear in my 4th citation above, but I will repeat for clarity.

quote:

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I initially confused the Mercury's with the Yamaha V-6 EFI's which have 3 such low pressure lift pumps, one for each set (top, middle, lower) cylinders.

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As an Aside, to the Aside to LHG, regarding the assertion that open-loop, non-programmable fuel injection engines like the Mercury V6 150-HP EFI are 'obsolete', I would suggest a closer look at how obsolete is defined before making such a characterization. See: http://www.merriam-webster.com/dictionary/Obsolete

Although the EPA may indeed impart regulations on a small and perhaps growing number of lakes and tributaries regarding the use of higher emission outboard engines, it will most certainly not render a single, higher emission engine "obsolete", at least as defined by merriam-webster. I have 2 such engines and have no intention of discontinuing their use, nor do I expect the EPA will enact any regulations regarding their use in the tidal waters I navigate anytime soon.