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  #1   IP: 151.199.27.201
Old 06-28-2009, 09:19 AM
Bacchanal Bacchanal is offline
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Angry Oily Plug - Backfiring?

I put in a Moyer exchange engine in my Apache 37 in 2007. After a while of diagnosing overheating issues, she ran great. All of 2008 she ran great. On start-up this season she ran really roughly before launch. #1 &#3 (new) plugs looked extremely fouled. Used MMO to free up what was thought to be stuck valves. Started running well. Launched boat. When I initially put her in gear I heard what I can only describe as a squeal. Kind of like a fan belt slip, but it wasn't that. Motored over to local harbor (not mine) with intermittent noise and left boat with local "boat genius" for a week. His diagnosis - transmission.

Here's the issue. It only makes this noise, which now sounds more like a "thump", when in gear and it's intermittent. I can rev the engine all I want in neutral w/o any noise. I disconnected the prop from the engine and put her in gear - no noise. Boat genius says it needs the drag of the prop. We finally had to vacate our borrowed mooring so we motored about 2 hrs to my harbor. Engine misfiring or backfiring or something as we went. Could not get above 1500 rpm. Also, RPM's drop about 100 when the noise is made. Motored at about 4 kts. Pulled plugs again. Only #3 is fouled. Cleaned and ran again. Plug now looks oily. All cyl pressure is between 95-100 with #3 being 100. There is also some oily residue in the exhaust pipe near the manifold.

What can cause oil in the cylinder? How else can oil get in except through the valves or rings? Am I looking at pulling a 2 yr old engine?
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  #2   IP: 76.7.153.46
Old 06-28-2009, 11:41 AM
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Marian Claire Marian Claire is offline
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If the oil ring in #3 is sticking in its grove and the compression rings are free it could be letting oil into the cylinder and still giving you the good compression #s.. Try MMO several times and see if it frees up. Is it backfiring out the exhaust or the carb? Just had an issue with backfiring and low RPMs. Dan S/V Marian Claire
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  #3   IP: 98.216.118.140
Old 06-28-2009, 02:16 PM
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Just curious. What sort of winterization process do you use. The fact that it ran fine last year and not this year makes me wonder what has changed.

Just laying up an engine for the winter should not cause the valves to stick or the rings to leak or the transmission to fail. I believe these sorts of things build up over time. Especially if we are talking about an overhauled engine. The fact that it ran fine last year sort of rules out an issue from the overhaul.

Quote:
What can cause oil in the cylinder?
Just thinking outside the box here:

Putting a small amount of diesel in the fuel tank would certainly oil up the plugs and cause misfiring.

Excessive MMO in the fuel system same thing I would guess.

Is the residue on the plugs oily or could it be coolant?

Figuring out if the engine is backfiring, afterfiring or misfiring would make a big difference as far as a diagnosis.

Backfiring = bang coming out the carburetor = too lean a fuel mixture.

After firing = popping out the exhaust = too rich a fuel mixture (possibly from the unburnt fuel from a dead cylinder) igniting in the exhaust system.

Misfiring = no popping just stuttering and running rough= a cylinder is not firing= no spark, no fuel, or no compression.
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  #4   IP: 38.102.24.128
Old 06-28-2009, 04:42 PM
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Since the engine ran OK when you laid it up for the winter, it seems that you would have to focus your efforts on the relatively small list of things that can happen while an engine is just sitting there (or being handled) over the winter.

Sometimes critters build nests in exhaust systems; corrosion develops around ignition parts, etc.

We really have no history of a transmission developing a problem like you're describing, especially during a winter lay-up. Is it possible that the marina folks got their sling around your prop shaft or otherwise damaged something in your drive train while pulling or launching your boat? Did anyone work on the engine over the winter?

Don
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  #5   IP: 173.48.187.150
Old 06-28-2009, 09:01 PM
Bacchanal Bacchanal is offline
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#3 Cylinder Problem

Thank you all for your advice & questions. This is driving me nuts.

The plug is definitely oily, not water or antifreeze. I got the #1 cyl. running well w/ MMO treatments, but the #3 is still a problem. I put in about 1/2 oz of MMO and let it sit from 10 min to 2 days. Probably did it 4 times.

Don suggested to check for critters in the exhaust. I haven't done that only because so much water is exiting, I don't know how a nest could be in there, but I will check now as I am running out of ideas.

When I first started up the engine it was definitely backfiring out of the carburetor with loud bangs and smoke out the flame arrestor. It now starts right up and seems fine until I put it in gear and it makes a thud-ump sound intermittently. Not sure if it is still a backfire as I haven't seen any evidence like before. When in gear, the engine is running at about 1100 rpm and when it makes the sound it will drop 100 rpm for just a second. After running for a very short time I re-inspected the previously clean, dry #3 plug and it is oily. The other 3 plugs are dry.

The exhaust pipe to manifold connection was not tight enough and I saw a little oily residue leaking out. I tightened the nuts, but that made no difference to the engine's running.

Winter lay-up was minimal. I flushed w/ fresh water and then antifreeze. As I have fresh water (anti-freeze) cooling, this really only affects the pump, heat exchanger and exhaust system. I didn't have MMO in the fuel and did not add it to the cylinders. I had about 6 gal of fuel in the tank w/ fuel stabilizer. In the spring, I added about 12 gal fresh fuel, a little MMO to the fuel and new plugs. I drained about a pint of fuel through the carburetor bowl. No visible dirt or water found. No other work done on the engine. I only remove 1 plug at a time, so I know I didn't switch the wires.

The exchange engine came w/ electronic ignition and I haven't loosened anything, so I'm sure it's not a timing issue. I do have a spare cap that I could use to eliminate a cracked cap issue. Spark tests show a good spark.

The boat is moved my hydraulic truck. Nothing touches the prop area.

I'm drawn to the idea of the potential oil ring problem and continuing the MMO treatments. It worked for the #1 cylinder. It will be a few days before I can get back to the boat. I'll give a try to whatever I can at this point. One guy told me to just get her out there and run her hard. She just didn't like sitting idle that long.
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  #6   IP: 71.252.20.96
Old 06-28-2009, 10:40 PM
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maybe?

I had some intermittent missing, and ran her hard (while missing) on the way home on a Sunday afternoon and she freed up. Right now, she is running rough again, but I think it is barnacles on the prop.

Maybe try running the crap out of her after an MMO treatment and see what happens. I know it feels bad when you jam up the throttle and she doesn't respond. Mine took about 20 minutes to open up and run well, after I her throttled up. She was not happy for that 20 minutes, but very happy for the 60 minutes afterwards!
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  #7   IP: 38.102.24.128
Old 06-29-2009, 07:31 AM
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One other isolated bit of information that might be relevant; backfiring out of the carburetor frequently results from sticky intake valves, and intake valves have almost no history of sticking unless inlet air is somehow reduced to the carburetor or elevated exhaust backpressure prevents the exhaust from flowing easily out of the boat (exhaust back pressure should be no higher than one and one half psi).

Don
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  #8   IP: 24.103.204.75
Old 06-29-2009, 08:01 AM
tenders tenders is offline
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Backfiring, to me, screams TIMING PROBLEM. And not just an out-of-adjustment timing problem, but a quantum timing problem.

That, plus oily plug, running rough, after winter maintenance, but good compression: are you SURE you have the spark plug wires spaced right on the distributor? Maybe you or someone else replaced the plugs or removed the wires to check something (or check the compression) and didn't put them back on in 1-2-4-3 order? Plug 3 is oily...that's one of the cylinders where the plug wire is installed out of order....

Try removing wire 3, and then wire 4, one at a time while the engine is running and see if things improve.

These sticking ring theories are plausible I guess but they violate Occam's Razor (simplest explanation that fits the circumstances is the most likely, so rule it out).
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  #9   IP: 173.48.187.150
Old 07-02-2009, 01:06 AM
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OK, will ck it all out

I will check and double check everything including the spark plug firing order. I didn't remove the wires from the cap and i only changed 1 plug at a time, but I'll eliminate everything i can as a potential problem. I will also check for any blockages in the exhaust. Where only 1 plug is fouling, it seems likely that that is part of the problem. I will soak the #3 cyl with MMO a couple of times and see what that does, too.
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  #10   IP: 151.203.41.159
Old 07-04-2009, 08:43 AM
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Smile It's always the simple things.

The first thing I checked was the firing order and they went off 1-2-3-4. OOPS! As careful as I was and convinced as I was that I couldn't have screwed that part up, I did. Put it back together and she ran very smoothly. Put her in gear and no "thud-ump" for the 10 min I ran her. Tried reverse, still good. Amazing. Thanks to all for insisting I check the basics. I've learned my lesson! Never did check for that nest in the tail pipe. I will check after todays run for that and if I still have an oily #3 plug. Happy 4th!
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Old 07-04-2009, 09:40 AM
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Congrats!
Time for sailing!
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  #12   IP: 142.68.244.175
Old 07-04-2009, 02:42 PM
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Good one, Tenders!
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