Fouled plugs

[Coork]

1999 Merc EFI 175 starts great wih new plugs and run ok @ wide open trottle. When idled engine misses and stalls, install new set of plugs and process repeats (plugs are oily and wet). This boat was purchased with out known history from a government agency. Fuel tank has not been pumped out and age of fuel is unknown. Where do I start,I have been tokd to start with replacing thermostat, then fuel, fuel lines and filter and beyond that to the dealer it goes.

 

[rickdb1boat]

Re: Fouled plugs

EFI injectors may need a cleaning or you may get away with adding some fuel injector cleaner to the fuel. Get rid of the old fuel and add new. Replace the Water Pump, T-Stats, fuel lines and add a Water Separating fuel filter. Drain and refill the lower unit, checking the condition of the fluid as you go. Check the compression to make sure you are working with a solid engine. All of this you can do without a dealer and a little I-boats help Ask questions here without hesitation, no matter how insignificant they seem. Get a good Manual if you plan on working on this motor or for just finding out what you need to do. Factory Manuals can be had at the link below:<br /><br /> web page

 

[Coork]

Re: Fouled plugs

Drained fuel tank today (all 60 gallons, put in my truck and van they ran perfectly). Checked compression and all within 5 PSI of each other. Replaced fuel line, fuel filter and, squeeze primer from water separator to fuel pump. Also purchased fuel pump rebuild kit, but did not install, as I was running out of daylight. Installed new sparkplugs, fueled up with 93 octane unleaded. Cranked engine, ran for 5 minutes at idle leaving no wake zone, and ran up river 2 miles @ ¾ throttle. Returned to ramp, engine stalled and would not restart... Pulled plugs, bottom port side plug fouled more than others, but all oil fouled. Spark to all cylinders, checked with inductive tester. Put in set of fresh cleaned plugs and engine still would not start until cranked with full throttle condition., engine ran rough and smoked badly for a couple of minutes then finally settled down. Engine would die when throttle is moved to idle position, would run @ 700 RPM in 1st detent position. When any attempt is made to put in gear engine dies. Pulled boat home and put muffs on fired right up and idled normally, able to put in gear without stalling. Water coming out of relief (pisser) is rather warm, but overtemp alarms do not sound. I will run with a portable tank next time out to insure that problem is not between main tank and water separator... What else can I try beside other than rebuilding fuel pump; I am at wit’s end. Am I correct in the assumption that thermostat would not cause this problem? Should I pull them and see what happens? This is getting real expensive, trail and many errors on my part, probably would have been cheaper to go to the service man.

 

[vinney]

Re: Fouled plugs

Fuel pump diaph. Or the engine is staying in the enrich mode(temp sensor).

 

[rickdb1boat]

Re: Fouled plugs

Coork <br /> <br />Almost everything I suggested HAD to be done anyway, as there was no history on the engine. So you are not wasteing money, but actually saving it by doing these things yourself. And there is no way all of that would have been cheaper at a dealer. At this point, I would unplug the temp sensor and see what happens. If no change, then at this point, you may want to take it in for diagnosis. But as I said, they would have hit you hard for what you have done. So don't feel too bad about the money you have spent...

 

[eurolarva]

Re: Fouled plugs

Your motor will run better on muffs then on lake because there is no back pressure with the muffs. You mentioned the compression numbers were within 5 digits but you did not post the actual numbers. When motor wont run under load I am thinking more compression problems then fuel. However if you had bad fuel one of your injectors could be partially blocked. I agree with rickdb1boat on having a pro look at it at this point. They can diagnose it then you can decide if you want to fix it or have them do it.

 

[vinney]

Re: Fouled plugs

Agree with Rick You have to start with a base line of service and that is what Rick said to do. If you don't know the engine you have to do the basic's first. Then if you still have a problem your not chasing your tail.

 

[Coork]

Re: Fouled plugs

Booat runs fine under load until I shut it down and attepmt to restart or idle. I will continue the trial and error. BTW I was not complaining about support from this site, you guys have saved me a bunch of money on my last few boats. I just want to get this sucker out chasing Spanish and Kings.

 

[Coork]

Re: Fouled plugs

Does Merc require a larger battery than normal ? I installed new battery with about 550 cca

 

[gss036]

Re: Fouled plugs

Is you upper exhaust port out of the water? Try tilting rhe engine up a ways and see how that works. If it doesm then your engine might need to be raised up on the transom. You don't sat what kind of boat etc?<br /> I run a pair of 550 Amp Deepcycle from Costco on my 200 Merc carbed, so I think you are ok there.

 

[Coork]

Re: Fouled plugs

My manual has not arrived yet and I would like to unplug the temp sensor. Only question is where is it ? BTW, history is unknown on this motor, but looks great, no corrosion, spliced wires or any other apparent damage. This boat was used by NC Wildlife enforcement in fresh water. This outfit has a rep for keeping stff in good condition, after set amount of hours (I believe 1000 engines are taken out of service and sold) Hulls may have up to 3 engines installed before being siold also.

 

[Coork]

Re: Fouled plugs

I did not mention when restarting after stall, engine smoke like Greyhound bus.

 

[jim dozier]

Re: Fouled plugs

Check for a leaking fuel pump diaphargm injecting excess fuel into the intake transfer port. That would be consistent with the poor idle (too rich) and fouled plugs.

 

[Coork]

Re: Fouled plugs

Checked compression this evening (1st evening without rain in a while) 92-98. Did something that I should have done from the start. Pulled spark plug wires while running. Engine hesitated and missed when wires pulled of port side. When plug wires pulled off starboard side no effect. Pulled plugs, plugs on port side damp, on starboard side dry. What kind of blockage or electrical problem could cause this fuel not to flow to one bank? I believe that when get I engine to run at full throttle I am getting fuel, but not at idle. However I have been known to be wrong before.

 

[Coork]

Re: Fouled plugs

Told today that Merc's when idling only use one bank on V-6 engines. I can not wait for my manual to get here..Never ever send anything book rate....

 

[Coork]

Re: Fouled plugs

Got new pump today, from Nick Korneff (Propelled Marine) at a great price and fast( saved me a couple of hundred bucks over Mercury of course I had the $600.00 pump) Installed and checked fuel pressure prior to attempting to start. Still only 27 PSI, at this point I got totally disgusted with myself and went down to my local Advance Auto and purchased another gage, checked pressure and BINGO at 39 PSI. Started motor and still ran like Crap, killed ignition and cranked to check plug condition, bottom plugs are dry, upper plugs are wet(it was about dark so I could not do any detailed checks and we have a little hurricane coming). I have pulled injectors checked with 9 volt battery all spit fuel, have 12 volts across positive to ground. Is it possible that the ECU is not hitting these cylinders ? Does a inexpensive method exist to check if the harness is going to ground to fire the injectors? I am now officially broke, after electrical fuel pump, fuel lines, mechanical fuel pump, dumping 60 gallons of suspected bad fuel, cleaning tank, 3 sets of plugs at $60.00 a pop, fly wheel puller, etc. I need help bad or will wait until next year on this monster. once this sucker runs I have worked on my last Outboard, I am a decent mechanic having rebuilt several Inboards and quite a few car motors as a hobby. <br />MERCURY (2.5L EFI SALTWATER) <br />Serial Number: 0T066822 Model Number: 1175423WD<br /><br /><br />__________________<br />I will cut the grass when I get back dear. RIGHT....

 

[Elmer Fudge]

Re: Fouled plugs

This motor probably just needs to be decarbed.

 

[LubeDude]

Re: Fouled plugs

You have never really told us what the WOT performance is (At least I never saw it). How does it run WOT, and what are the numbers, WOT RPM, Speed, and prop pitch.<br /><br />Elmer has a good point, concidering the compression #s you gave. My 150 has about 120 #s per cylinder.<br /><br />Also, use NGK plugs.

 

[Coork]

Re: Fouled plugs

I may have found my problem. When checking pressure it would build up to 39 PSI then bleed down to 0 PSI within 2 seconds after fuel pump turns off. Pulled ECU and fuel management assembly cover and jumped ground to fuel pump. Observed fuel leaking from top of fuel rail down length of tube. I would imagine that this is an abnormal; condition, and could cause the plug fouling that I have been experiencing. As stated if I do not idle and go straight to full throttle I have no problems, (engine able to handle the excess fuel?)But if I idle for any period it fouls cylinder three and cylinder four. Cylinder Five and six are lean or even possibly normal (as I have not had any thing to compare them to). I will pull rail tomorrow and try to pin point source of leak, appears to be coming from press fitting on top of rail. Any suggestions or comments? My theories have been out to lunch before, and I would not be surprised if that is still the case. If fuel rail is the problem, can they be obtained from any place other than mercury?<br /> Engine has been decarbed.<br />

 

[Coork]

Re: Fouled plugs

Lean condition Cylinder # 2 ???? <br />Repaired leak in fuel rail today, problem was cracked o-ring in joint between fuel rail and joint. Fired engine up and repeated earlier problems. Grounded out ignition and checked plugs for fuel per manual, all plugs wet except # 2. Number 2 did not show any traces of fuel or oil. Pulled cover to air box and checked all injectors with 9 Volt Battery, and all injectors sprayed what appeared to be copious amount of fuel. Pulled fuel rail and cranked engine, once again injectors sprayed tons of fuel. Reinstalled fuel rail in air box and checked #2 plug was damp, but not were near as wet as balance of plugs. I realize that visual observations of fuel sprayed by injectors are not accurate, but # 2 did not seem much different then the rest. Checked compression, about 120 PSI per cylinder, all within a couple of points. I am going to send my injectors to Tony B. for testing and going to be, borrow or steal stuff to do leak down test. Any suggestion of anything else to check while waiting for injectors return? Could reed problem cause this? Should I pull heads and look for cylinder wall damage. I have replaced fuel lines, water separator, fuel filter, mechanical fuel pump, electrical fuel pump, squeeze ball, gasket between air box and reeds, and all o-rings in fuel separator and fuel rail.<br /><br /><br />__________________