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Fouled Plugs

chuckhanson

chuckhanson

Regular Contributor
"My boat was not used in 2005

"My boat was not used in 2005 and 2006 due to a heavy travel schedule. You can guess that I have had my hands full getting everything ship-shape again. The remaining problem is that although the port engine runs very smoothly, it is fouling plugs quickly. The last set lasted 5 hours. All of the plugs were uniformly dry with black carbon build up. I have run all of the stale gasoline out and about 100 gallons of fresh through this engine. There is no water in the gasoline. The ignition timing is set at 10 degrees BTDC. I cleaned the flame arrestor with carburetor cleaner 20 hours ago. The starboard engine is not having any problems. It only took one change of spark plugs about 30 hours ago.

Some particulars on the boat, its use follows:

Boat:
* 1984 50 foot Gibson Houseboat, owned since 1988

Use:
* Recreational in fresh water
* 14 years on the Mississippi River and 9 years on the Tennessee River
* Most of the hours run at 1400 to 1800 RPM (I don’t race the Gibson)

Engines:
* Model CH350 454 CID
* Starboard Left Hand and Port Right Hand
* 1160 hours on each
* Raw water cooled
* Carburetors:Rochester Quadra Jet (17082403; Both rebuilt in 2003 by Carburetor Specialist in Alpharetta, GA
* Electronic Ignition
* Electric Fuel Pumps
* Huge Water separators/filters

Any thoughts on what the problem is would be appreciated.

Chuck"
 
You are running too rich. Chok

You are running too rich. Choke might not be operating properly or choke pull off is defective or carbuerator jets are too rich.
 
"I am on the boat today and ca

"I am on the boat today and can check to see if the choke is opening properly. I am not a carburetor man so I had a mechanic adjust the idle jets. It idles nicely. Can the "running jets" be adjusted or is this something that has to be done on the inside of the carburetor?

Is there a possibility that the ignition on this engine could be weak causing incomplete combustion? If so, what could be the reason? Can this be checked?

Thanks,

Chuck"
 
"Ignition wise you would get a

"Ignition wise you would get a misfire symtom and/or the plugs would be unevenly fouled. Also check that the backfire flame arrester is not dirty and restricting the intake of air.

True, you should rule out ignition problems before before monkeying with the carbuerator but nothing you have said yet indicates an ignition problem. A "weakness" in the ignition system will cause cause either a comeplete shut down of the engine or misfire under some or all running conditions. Although a weak spark can indicate a deficiency in the ignition system, inside the cylinder there only presense of a spark or absence of a spark. The concept of stonger spark giving you more power is a common myth leading to the rip-off of "super plugs" such as multi-electrode gimmick plugs. Newer (last 25 years or so) ignition systems acheived better performance from spark plugs but it was achieved by engineering the ignition system to enable the spark plug to have a larger gap but the plugs themselves are not, other than gap, different."
 
"The choke is operating proper

"The choke is operating properly and the flame arrestor is clean. I have to believe it is in the carburetor. Today I removed the carburetor and will send it for rebuilding this week. I noticed when I removed it some carbon build up directly beneath the carburetor in the intake manifold. I wonder, could it be varnish build up which got burned during a backfire through the carburetor?

I will let you know if the carburetor was the problem after I get the rebuilt installed and run a few hours."
 
"Hey, Chuck:

If the carbs a

"Hey, Chuck:

If the carbs are still in place, you cna save yourself some $$$ by having a mechanic perform the following test:

1. Warm the engine fully and let it idle.

2. Screw the idle mixture screws all the way in.

Did it slow dramatically or stop? If so, the carb is flooding. If it did not the carb is working fine so save your money.

Jeff"
 
Thanks Jeff. I had a mechanic

Thanks Jeff. I had a mechanic adjust the idle last week. I observed hoping to learn. He started by setting the two jets to 2 turns. He then screwed them in until the engine lost RPM then backed off. At one time he screwed them in to the point the engine died. I took the carburetor off this afternoon and brought it to Memphis. I won't be able to go back to the boat for two weeks.

Do you have a recomendation for a rebuild shop?
 
have you run Seafoam throught

have you run Seafoam throught the intake? You may have a build up of varnish in the combustion chamber and on back of intake valves. Seafoam is good stuff and should clean it up well. The poor quality petroleum sold these days is dirty fuel
 
Thanks Stephen. Now I have se

Thanks Stephen. Now I have sent my carburetor off for rebuild. I didn't try the Seafoam. I am afraid that I am the guilty one. I let the gasoline rot in my tank for two years. It is all gone now. I hope I will get a chance to start again. I reckon I will have to deal with any buildup on the valves and in the manifold.

Chuck
 
I used the seafoam on my port

I used the seafoam on my port engine during another issue I had a few weeks ago. The smoke was very very dramatic and it did cleanout the varnish under the carb mounting area so it may have done even more than that. I am pulling the intake manifold next week and will identify even more if it did it. Seems like neat stuff
 
I just got word back from the

I just got word back from the shop that is rebuiding my carburetor. The short of it is that the carburetor was really dirty. The float needle could not shut off the fuel completely leading to a rich mixture. I will reinstall it on 11/19 and see if that resolves this pesky problem. I will let you know the results.

Chuck
 
What a difference a carburetor

What a difference a carburetor rebuild makes. I did reinstall it on the 19th. I pumped the accelerator three times and it started in the first revolution. It idles at 800 RPM right out of the box. How sweet it is. I have run it for about 8 hours now and all seems to be ok. I will turn to the starboard engine next.
 
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