Carbon deposits on plugs

[Moby]

This may have been discussed before but I couldn't find anything here or on the Catalina 30 site.

I bought a Catalina 30 with an A4 back in December and motored up to Maine in April. The A4 ran like a top.

Now, back at the ranch, I mean marina, I have been out about 16 time since the delivery and last time out the engine ran really rough. Pulled the plugs and lots of carbon deposits. Changed the plugs and it runs smooth again.

If I just use the engine to get in and out of the marina so that it never reaches the 160-165 degrees nominal temperature, how do I prevent the fouling? With the price of gas is it cheaper to replace the plugs or run the engine longer and harder to burn the carbon off?

Points and distributor cap looked great. Idles smooth with new plugs. Just little white puffs in the exhaust.

Thanks for your help! Some day mine will go from rust bucket to pinup!

Moby

[David Masury]

The next time this fouling happens... replace the Champion plugs with Autolite 437's... same gap as the Champions. The problem will go away.

David

[Don Moyer]

Moby,

Your plugs shouldn't need replacing every 16 hours, even given your operating conditions. I suggest you check your compression. Any compression values over 85 should be OK. I'd also check for the strength of the secondary discharge from your coil by removing the coil lead from the distributor cap and hold it close to the head while cranking the engine. You should be able to stretch the arc to at least 1/2". If those items are OK, I'd recheck for proper ignition advance by loosening the distributor hold-down bracket and slowly rotating the distributor a small amount in each direction to see if you can gain a bit of RPM. If you can, retighten the hold-down bracket in the location of max RPM.

Being relatively new to the Catalina 30, you might not have seen the attached technical notes which you might find useful.

Don

[Moby]

David,

Are the Autolite 437's a hotter plug? Someone else suggested I switch to a hotter plug.

Don,

Thanks for the suggestions. I will check each one and read the notes as well.

Great website and forum! Thanks for sharing your knowledge!

Moby

[High Hopes]

Moby,

I installed plugs without checking the gap. The gap was woefully to small and I got lots of carbon build up.

I'm not sure if this willl help, but in order to get my A4 running smoothly, I had to set the timing (17 degrees at 1600 rpm), gap the plugs, lean out the fuel mixture with Don's needle valve kit, and set the idle for 800 rpm and fiddle lots with the carb idle mixture valve. I also added a strong spring to the carburetor throttle to hold it shut. The throttle seemed to have two idle speeds when the shaft was wiggled. Oh yea, I pulled out 2 quarts of oil. (I now do oil changes with with three quarts. I was using 5). Plugs run clean now.

Steve

[Moby]

Thanks Steve. All good things to check. The plugs I pulled were the ones in the boat when I bought it and I did not check the gap but I did gap the new ones I put in to 0.035 in. I have not played with the mixture or timing yet. I really want to get through the summer without too much work on the engine and then pull it in the fall. I am not sure if I need a rebuild yet (haven't checked compression) but it certainly needs paint and a good going over (replace all hoses, add some upgrades...). Should keep me busy over the winter (that's our built-in maintenance period up here in Maine).

I have also decided it would be a good thing to zoom around the harbor once to get the engine warmed up and burn off any carbon before heading in. I think my problem is just like a car that drives 2 miles to work and back in the winter, it never gets warm. I also might want to check the choke to see if it is sticking.

This is my first boat with an inboard engine so I have lots to learn! This forum is a great resource!

Moby

[High Hopes]

Moby,

I puirchased a 1975 Sabre 28 in November last year. It is my first inboard and my first boat. Quite an experience! Maybe someday, I'll actually sail her.

Steve

[Moby]

One question that may be of interest:

Do you think that the carbon deposits could be the result of going from E10 (ethanol) gas to gas with MTBE? I moved the boat up from Connecticut to Maine this spring and am pretty sure E10 was used on the way up. Once I reached Maine I continued with the gas in the tank till I was about 1/4 full. I then filled with MTBE gas and had the problem shortly thereafter. After changing the plugs I have motored enough to use half a tank with out any problems. Of course, due to the amount of motoring, the engine has been run up to temp for good period of time so I am running differently than just going in and out of the slip.

Moby

[Moby]

OK, this is beginning to bug me. I put new plug in, checked the timing by warming the engine up, putting it in gear (tied to dock) and giving it some gas. I rotated the distributor one way until it started to run rough, went the other way until it started to run rough, then put it in the middle of those two spots. I checked the spark by pulling a plug and checking the gap to the engine block, got good spark.

Ran the engine for about 5 minutes, pulled a plug and it was loaded with carbon.

Oh, BTW, before I did all this I also pulled out some oil because I think I was over full. Now reads between add and fill. Didn't seem to make a difference.

That leaves me with the carborator. The choke seems to operate OK. Could it be the mixture?

[Moby]

Well, compression is OK. 100-105 psi in all the cylinders. We checked the choke again by removing the whole flame arrestor assembly and it looked like it was not opening all the way so we adjusted the cable so that it will. Ran the engine under no load, mostly idle for 5 min and plugs had carbon deposits. Running out of things to try!

[Moby]

Tried running the Champion RJ12C plugs. No difference. Ran around the harbor for about 20 min. at 5 knots and let the temp get up to about 180F. Still carbon fouled. Check the spark going to each plug and it was good. I normally operate at about 160F but ran it up to 180 to see if I could burn off the carbon. I usually flush the block with fresh water after running that hot.

At idle we pulled the spark wire on each plug, one at a time, and the idle speed/sound did not change. I even pulled 1&3, 2&4 and it starts right up and idles fine. Sounds a little different but not lugging or sputtering.

[Don Moyer]

How fouled do your plugs get? Do they foul to the point of the engine missing or running poorly? If there are no performance issues with your fouling, you may simply have a slightly rich fuel mixture. I would try to give the idle mixture adjustment an arbitrary 1/4 turn in a clockwise direction. If the engine still idles OK try another 1/4 turn. If you get to a point where the engine idles poorly, go back to the previous setting.

You can also install an adjustable main jet and lean your mixture. There are some carburetors from the mid-seventies (prior to the advent of the so-called five-bolt carburetors) that tended to run rich due to poor internal pressure regulation.


Don

[Moby]

Don,

Thanks for the reply. Yes, the plugs will get to the point where the engine will run rough and not have power. Usually after about 1-2hrs of operation.

I just found the "5 bolt carburetor" article and will check mine. The thing that baffles me is that the engine ran great for 5 days motoring up from CT. If it was a high speed mixture issue I would have fouled plugs on that trip. Why all of the sudden is it running rich now?

How many cylinders can an A4 run on? As I mentioned I pulled 1&3, 2&4 alternatively and the engine started and sounded pretty good. Maybe I'll try pulling 1,2,3 or 1,2,4.

Moby

[High Hopes]

Moby,

I read your postings and I'm not sure I understand everything.

Is it only when idling that you have soot showing up on the plugs?

Was it only after you changed the gas type that you had the problem?

Do you have a tachometer? (Are you really idling at 800 rpm?)

Did you drain all the oil out and only add 3 quarts back in? (I would ignore what the dip stick indicates.)

Do you have a timing light? I think it is best to set the timing to spec and make sure the distributor is following the advance curve spec (available on this site). I picked a midpoint and set it (while not under load). This was critical to a good idle.

Can you stall the engine at idle if you open or close the idle adjustment all the way? You be able to do this.

Did you rebuild the carb? The upper housing on mine didn't mate properly with the bottom housing. It was warped and leaked (air and gas). My main carburetor was a #24 which was too large. Do you know what yours is?

[Moby]

Steve,

Thanks for having an interest in my problem. After searching this forum I found several messages wrt carbon fouling and some did not post the final answer to their problem.

1. Idle or at full speed at 180F I still get carbon fouling very quickly, anywhere from 5 min to 1hr depending on when I pulled the plugs.

2. As far as I can tell the engine ran fine until I filled up in Maine the first time with MTBE. I'm pretty sure I was getting ethanol on the way up from Connecticut.

3. I don't have a tach installed yet but will put one in tomorrow to adjust the idle mixture and rpm. I seem to get fouling when I idle or go at top speed.

4. I pulled a little over a quart out to get it between the full and add marks on the dipstick. The oil is black after only a few hours but my friend who has an A4 says that is normal. He think the engine sounds OK, just a ticking which he hears on his too. My idle speed is a little low according to him so I will check it tomorrow with a tach.

5. I don't have a timing light and my flywheel is covered. I don't have access to remove the cover. That is a sweet setup you show in the picture. Looks like the engine is off the boat though. If not, you have great access!

6. I will try tightening the idle mixture screw to see if it will stall when it is too tight.

7. I just bought the boat and I don't think the carb was rebuilt although it is not painted so it might not be original. I just found out about the 4 bolt vs. 5 bolt carb so I will check for gaps between the body sections. I will take copious pictures of the carb tomorrow.

Thanks for your help!!

[High Hopes]

My money is on #2 if everything worked fine before that.

#4 I pulled all the oil out and added 3 quarts back in to mine. Is the oil level different than before when you didn't have the problem?

#5 The engine is off the boat.

#7 Here is a picture of my carb before the rebuild.

Good luck. - Steve

[Don Moyer]

In troubleshooting, it's always productive to consider very seriously anything that changed between the time the engine last ran OK and the time the problem began. In your case, Mixing Ethanol and MTBE fuel was apparently the only such change in your operating conditions.

Mixing Ethanol and MTBE fuel was one of the items that Boat US cautioned us to avoid several years ago, since it was known/believed to cause problems which related to carbon build-up on valves. This condition would relate in a general way to your plug issue as well. If it's not too difficult, you could rig up an auxiliary fuel supply to see if your problem goes away. In your case, you should know in 15 minutes or so rather than waiting till you refuel enough to have pure MTBE fuel.

If the problem persists after getting rid of your Ethanol/MTBE fuel mix and all of the other things you and Steve are talking about, you may have to consider elevated exhaust back pressure (which would handily explain your symptoms). I don't know why your back pressure would change just after your trip, but then we would have trouble explaining why anything changed just after your trip. All of which gives credence to resolving the Ethanol/MTBE fuel mix issue first.

Don

[Moby]

Maybe this video will help although it sounds OK to me.

http://video.google.com/videoplay?do...62302464&hl=en

The spark plugs were just replace and the engine was warm. I know, it's not pretty (yet) but I just want it to run. I almost didn't make it into the slip yesterday because it died at the critical moment. I went out with clean plugs and came back with this:


I think it's the gas so I'm going to try some Stabil additive.

[blackdove]

Hi Moby,

I think that Don hit the nail on the head...a combination of ethanol and MBTE is not conducive to an engine that doesn't run pretty hot. Adding the Stabil may just further complicate the problem. The chemistry of these additives is pretty neat and works well individually, but when mixed, it's similar to an oil/vinegar mix and creates phase seperation in the fuel tank. It could also be generating some moisture depending on the head space in the tank.

My recommendation would be to remove the existing fuel mixture and start fresh. Otherwise, your fuel tank is going to resemble a Gilbert Chemistry set and it will confound solving the soot issue. Hope this helps.

Blackdove

[High Hopes]

Originally Posted by blackdove

Hi Moby,

Otherwise, your fuel tank is going to resemble a Gilbert Chemistry set and it will confound solving the soot issue. Hope this helps.

Blackdove

This is completely off topic, but Whoa! Turn back the hands of time! - A Gilbert Chemistry Set. I had two of these. One of the frist things to do was to mix everything together and see what happened. One got useless gunk (like Moby's gasoline problem?). I think I was 9 at the time.

Thanks for the flashback trigger, Blacky.

Steve

[Moby]

Blackdove,

Yes, I am concerned about the chemical goop (oh yes, I had a chemistry set too!). I have ethanol, mtbe, lead substitute, MMO, and Stabil. I figure I have about 10 gallons left in it so I might just siphon it out and burn it in the lawnmower (see if that chokes the mower!). I just want my boat to have a reliable engine so I can get in and out of the marina without bashing into things.

I'm wondering if I should rebuild the carburetor. Is is possible the main jet is gone or corroded open? Could the float be flooded and the bowl getting too full? Could that cause it to run rich?

My other concern is once I solve this problem how do I get the carbon out of the engine?

With all of you guys helping me I'm sure I'll get to the bottom of this issue!

P.S. Did you watch the video? Does the engine sound OK?

[blackdove]

Hi Moby and Steve,
Yeah, I did the same thing...mixed everything together and got one heck of a gunky mess.

I don't think I'm qualified to speak about the carb...that's a question for those who really know engines, etc. The mixture of the stuff in the tank is almost like an oil fuel rather than gasoline. It is possible that it could be creating carb problems but I don't know that.

I do know that the combination of the group in your fuel tank is going to continue to give you fits. Back to my original rec...empty it out and start afresh with MMO only. My understanding of the chemistry here is that it should help to get the carbon out of the engine (probably more gunk form than soot-like). I would also think that once the engine gets running again in a good mode, the carbon/gunk in the engine would burn off.

Again, hope this helps.

Blackdove

[sunnnnseeeker]

I would focus on getting good gasoline to the engine and give it a chance to get back to normal. If after some running with clean gas if it doesn't straighten out then you can focus on the other issues, if they still exists. I think the engine will clean itself up.

[High Hopes]

Moby,

Take our collective recommendation. Get some fresh gasoline, disconnect your tank, run your A4 fuel line into the fresh gas, and see what happens.

Steve

[Moby]

Thanks all. I will get fresh gas and let you know what happens. After talking with some other boaters they buy gas at the gas station and bring it to the boat. The gas is fresher and not prone to getting water as much as a marine pump (just don't go to one with a car wash!).

I will probably drain the tank into some containers (proper ones of course) then fill with fresh gas.