What does this mean? (Sparkplugs)

[TomG]

After a nearly two year stint on the hard, Patina is back in the water. I tested everything I could before putting her back in the water, but some things I just had to check after launching. This afternoon, I was able to get the engine running, quite smoothly, 40psi oil pressure, 140 degrees F, idled nicely, all that good stuff. After running the engine under load and at idle, in gear and neutral for close to 45 minutes, everything seemed fine. No leaks, no stopping, no surging, no apparent missing. For grins, I pulled the spark plugs just to take a look. What I found, you see above. I immediately did a compression check, and all four cylinders were within a few psi of each other (on the low end at 80 psi, but I'm using a compression tester from Harbor Freight, so caveat emptor). Cylinders 1 and 2 look very oily while cylinders 3 and 4 look like they're supposed to. I'm a bit perplexed... I was thinking stuck valves on 1 and 2 or a bad head gasket between the two, but their compression was exactly the same as 3 and 4, which look fine. I did figure out that I was running a cooler plug than Don recommends in the MMI manual (an 8 vs. a 12), but the differences between cylinders are pretty striking, with no other apparent symptoms.

What does this mean? Anything?

[Dave Neptune]

Probably a stuck ring.

Tom, number 4 & 3 look a bit lean but good. Number 1 & 2 look a bit sooty. If you touch the "black" is it sooty or more oily and wet? Sooty could be the carb but doubtful or possibly a vac leak. If they are a bit oily you have a bit of oil getting into the cylinder. How long since an oil change? Since you said it has sat for a while I will bet that the rings are a bit stuck.
Add a bit of MMO to the cylinders (1 teaspoon is enough in each hole) and let it sit. Add some MMO or Outboard 2-stroke oil to the gas at about 150~200:1 mix and run a few gallons through her. Things may improve over a short time.
What plugs are you using?
FYI the plugs that are usually trouble are actually 4 & 3.

Dave Neptune

[TomG]

Dave,

Thanks for the quick response. I am using Champion RJ8C's at the moment. Looking through the A-4 Bible, I notice Don recommends the RJ12C plugs. The engine is a MMI rebuilt in 2008. Over the winter, fearing stuck rings and valves, I would shoot a couple of squirts of MMO in each cylinder every few weeks in hope of loosening up any thing stuck before I ever turned the engine over. Oil was changed about two months ago, but the engine was never really run (other than a few minutes here and there) since it was changed. I have added MMO to new fuel.

Because this engine is on a Tartan 30, water intrusion into cylinders 3 & 4 (especially 4) is a chronic problem. I have largely eliminated this potential by going with a standpipe, but was thinking if I was going have an issue, it would've been with three or four. Odd that it's 1 and 2.

Thanks for the advice... I'll keep an eye on things.

[roadnsky]

Tom-
You might also want to consider using the AUTOLITE 437's.

Quoted from the MMI online catalog:
"These plugs can be used as suitable replacements for the Champion RJ12C. They have a heat range slighly above the Champion model and as such, they may give slightly better performance in engines that tend to foul plugs on a regular basis."

http://www.moyermarine.com/cgi-bin/shopper.cgi?search=action&category=IGLM&keywords=all&template=Templates/B000_storebuilder.html

[TomG]

Thanks Jerry! I'll definitely keep that in mind. I just finished moving the boat about 12 miles this morning. It's the first time the boat has been in the water in over a year and half. We were very lucky in that we were able to sail very nearly the whole way, but the mighty A-4 performed flawlessly! I had a little smoke come off the new hot section and heat wrap, but the engine purred very nicely in and out of the slip. We motored into the wind for about 15 minutes approaching home port and were making 6 knots without even trying!

It's been a wonderful morning!

[roadnsky]

...It's been a wonderful morning!

Any day on the water is better than...