Sparkplug #5 clean...

[Merc90HPnewbie]

Ok so I went to 'winterize' the boat this saturday. Long story short I got the engine started, removed the fuel line, and sprayed Quicksilver "Quick seal" (or whatever their fogging spray is called) into each carb. I have a 1985 90 HP straight 6 o/b (three carbs). I let the engine run until it died of fuel starvation. Oddly it was running pretty well on the diet of whatever gas was left in the carbs and the fogging fluid I was spraying in. I had posted here a long time ago about the wisdom of doing this (will some carbs run out of gas before others, making some cylinders pump up and down with no lubrication? The response was a definite.... "maybe" so I figured I would try it out). Then I go to pull the plugs and put the fogger in each cylinder. All the plugs have at least some brown oil on them which was OK considering I sprayed a lot into the carbs, but the fifth one from the top was totally CLEAN. I mean, it almost looked like I just got it from the store. Unfortunately I had never pulled all the plugs before so I dont have much to compare it to, but it made me nervous. And that cylinder was definately running hotter than the rest. Putting my hand over the open sparkplug holes, all the rest were cold and this one had a noticible amount of heat coming out. Not so hot I couldn't stick my pinkie in there but it was warmer than all the rest.<br /><br />So, is this a case of one cylinder running out of fuel (and the accompanying lubrication) and getting a little warmer? Or could this be a dead cylinder? What should I look for? <br /><br />Thanks for any replies. I'll try not to freak out about this all winter <br /><br />PS Some grey (gray?) sludge oozing out from exhaust after the above procedure. Is it safe to assume that's just partially burned foggoing oil?

 

[greasemonkeyozi]

Re: Sparkplug #5 clean...

Make sure that your 5th cylinder is getting spark. It shouldnt look all that new if you've taken it out a couple times. <br /> As far as defogger, after you run it in all carbs, take your spark plugs out and spray some in eack cylinder.

 

[vidar]

Re: Sparkplug #5 clean...

HI! if the plug is very clean...you can have a water leak iin that cylinder..plug looks like its steamcleaned....most likely bad head gasket....

 

[The Marine Doctor]

Re: Sparkplug #5 clean...

Lets clarify that your engine does not have a head. This will eliminate the blown head gasket theory.<br /><br />Check the compression of that cyl as well as the spark.<br /><br />Grey sludge is not storage fog...it comes out white.<br /><br />TMD

 

[Merc90HPnewbie]

Re: Sparkplug #5 clean...

Ok I guess I need to buy a compression tester. Can anyone recommend a unit with a decent number of adapters, and how much should I be spending on it? Do those gauges with the rubber cone ends (no adaptor needed) work accuratley? What thread size are my sparkplug holes?<br /><br />For Spark testing I can just pull that plug out and have someone hit the starter while I look at the plug face right? As long as I ground the plug body somehow.<br /><br />MGR: No problem, I did that, carbs first, then I pulled the plugs to spray inside the cyls. That's when I noticed #5 clean and warmer than the rest.<br /><br />TMD: Any idea what thay grey sludge is then? Also, my theory of running out of gas/oil unevenly- does that make sense? Or would it have to happen on BOTH cylinders fed by one carb?

 

[Kenny Bush]

Re: Sparkplug #5 clean...

Sounds totally like a bad water head gasket. Be careful........ A lot of bolts are broke getting the plate off. Drill, Tap, get new bolts; hopefully it won't happen, but that is your highest risk...

 

[The Marine Doctor]

Re: Sparkplug #5 clean...

I suspect that a compression test will tell you what the grey sludge is. I suspect aluminum off the sides of one of the pistons.<br /><br />You can buy a comp guage for $25, at Napa.<br /><br />TMD

 

[Merc90HPnewbie]

Re: Sparkplug #5 clean...

Gaak!<br />Ok I am getting a compression tester tonight if I can get to NAPA before they close.<br /><br />Let's say I do the test and find out the #5 cyl is low, it lost cooling and overheated so the piston &/or cylinder wall got scored/fried/etc. Is the motor toast? Or can I hone down the cylinder and put a slightly oversized piston in there?

 

[Kenny Bush]

Re: Sparkplug #5 clean...

Man if you toasted a cylinder, you will have to tear down the whole motor. On the straight 6's, the head is built onto the block. That means that you must pull the crank and pistons(some people leave pistons in) to get to the cylinder to inspect. The V6s can be inspected by just pulling a head. Not so on the straight six. Do your compression check and post results. The compression reading will tell us what direction to go.

 

[Merc90HPnewbie]

Re: Sparkplug #5 clean...

Anyone know what adaptor size is needed for this motor? 10,12,14,18 mm?<br />Thanks

 

[rickdb1boat]

Re: Sparkplug #5 clean...

NGK- BUHW- 14 MM

 

[Merc90HPnewbie]

Re: Sparkplug #5 clean...

Alright, I did the cylinder pressure test. I guess it would be considered a 'wet'test as I assume there was still fogging oil in all the cylinders. I was trying to rotate the motor by hand, wrapping a rope around the flywheel and pulling, but my readings were all over the place (cyl 1-35, cyl 2-90) so I gave up on that and hauled the battery out to the boat. Cranking for about 2.5 seconds on each cylinder, I repeated each cylinder twice. I was suprised by how consistent the readings were on the individual cylinders, and also suprised how different the cylinders were from each other:<br /><br />Everything in PSI<br />1=162.5<br />2=180<br />3=195<br />4=160<br />5=160 (!)<br />6=137.5<br /><br />So the cyl I expected to be 'bad' was right in the middle. The 6th cyl was low and the 3rd was high.<br />Also they all held the pressure for a considerable amount of time (shouldn't the lower ones bleed off faster? Or is there a check valve in the meter that holds the peak reading?)<br /><br />Difference between highest and lowest =57.5<br />Average= 165.8<br /><br />So what am I looking at here?<br /><br />Thanks experts!

 

[The Marine Doctor]

Re: Sparkplug #5 clean...

You might want to take the covers off the Starboard side and have a peek at the pistons.<br /><br />TMD

 

[Backlash]

Re: Sparkplug #5 clean...

You've got a real variance between those cylinders (not good). I'd de-carbonize & then run the compression test again. By the way, there is a check valve in the compression gauge so you can't use it to do a leakdown test. How was the motor running recently? <br />Backlash

 

[Merc90HPnewbie]

Re: Sparkplug #5 clean...

TMD: I noticed a plate/cover on the port side when I had the cowling off. I'll have to check the manual to see what covers you're referring to. How much of the piston could I really see? Just through the exhaust port in the cylinder? I have a fiberscope I could stick through the sparkplug holes, maybe I'll try that today.<br />Anyway, what would I be looking for? Cylinder scoring? Burnt piston?? Broken rings?<br /><br />Backlash: What's the best way to decarbonize- Spray some aerosol Deep Creep thru the plug holes, let it soak, then start engine? Or is there a more thorough method? <br />I found a schrader valve in the end of the adaptor hose. If I took that out I think the gauge would show the true pressure in real time.<br /><br />The motor was running great last time I took it on the water, a little more than a month ago. Last week when I winterized it it was hard to start (though this motor is generally hard to start cold) and seemed to have a little extra vibration while running. Could just be my imagination though.<br /><br />When pulling it over by hand there seemed to be a rough spot, although I always had the pressure gauge installed in one of the cylinders. I will try again with all plug holes open and see if I still feel that.<br /><br />Thanks again for the advice. I'll post more when I find out more.

 

[Merc90HPnewbie]

Re: Sparkplug #5 clean...

UPDATE:<br /><br />Checked for spark on the plug wires #4,5,6. Got spark on 4 and 6 but NOT 5 (I used one of the other plugs, not the one that originally came out of #5). I don't know how long it's been this way. I looked at the #5 plug wire back to where it connected - it was in very good condition, no breaks in insulation or carbon traces - but that's all I knew to do.<br />I have to say everything under the cowling of my motor is in very good condition, no corrosion or gunk- howver I know this doesn't mean anything about the condition of the electronics.<br />What now?<br />Thanks

 

[profish00]

Re: Sparkplug #5 clean...

drive it like you stole it!!!

 

[Kenny Bush]

Re: Sparkplug #5 clean...

Do the "Deep Creep" decarbon, and run it out for at least 15 minutes. Then recheck your compression. Your readings are very high and out of whack..... Looks like you have a lot of oil in those cylinders, thus increasing the reading.... You may be on to something with no spark on #5. Could be a dropped coil. First get that motor running and up to temperature, after all the oil is burned out, recheck the compression readings. They should be around 120 lbs. I tell people to spin the motor over for about 3 to 5 seconds, or watch the guage and wait until it reaches maximum compression reading. I still say there is no way to inspect (hardly) on the straight sixes. Take new reading and post results.

 

[Merc90HPnewbie]

Re: Sparkplug #5 clean...

Hi Bushcat<br />I can do that no problem, but with no ignition going on in cyl #5 would it burn off the oil or just gum up the works?

 

[G DANE]

Re: Sparkplug #5 clean...

Hi Merc 90<br /><br />I wouldnt recommend you to run it much, as no ignition on # 5 will create a washout situation. The way 2strokes are lubricated is by the oil left over when the gas is burned. No combustion makes gas wash lube thin. Try to swap nr. 5 coils charge wire to another coil and see if it fires. If it does, get a new coil, as the compression on all is above 100, they will all run. I think there is lots of fogging oil or oil in your cylinders. Get it to fire and run the oil and decarb out. I think you will end up with equal and good compression on all.