Spark Plugs

[Mike250]

Back in the day I used to clean fouled plugs and it seemed to work fine. Now I read (and hear) that once a plug is fouled it's better to just put a new one in it's place.

I just had my 2005 496 mag repaired (OWO060256) thinking I had a fuel related problem and the mechanic stated it was a "bad" plug. I had just cleaned and gaped all plugs when I was trouble shooting the motor but he said once their fouled their trash... He also stated that 38-40 psi fuel pressure is OK even though the specification is 42-44psi. I'll take his word on that since he claims the motor is now running fine.

What's your experiance with fouled plugs?

 

[Bondo]

Re: Spark Plugs

but he said once their fouled their trash...

Ayuh,... That I Agree with,....

He also stated that 38-40 psi fuel pressure is OK even though the specification is 42-44psi.

And That,.. I Don't Agree with...

If 38/40psi was Alright,... That's what it would be spec'ed at....

 

[Big Boat Bay Buster]

Re: Spark Plugs

I tend to agree on the spark plug thing. I had a motorcycle with a weak ignition system. On a cold morning the plugs would sometimes foul and bike would not start. I would clean em up till they looked like new, only to have them foul out the next cold start. Only cure was to replace the plugs. The bike trained me to replace the plugs every fall,--Chris--

 

[Don S]

Re: Spark Plugs

I do believe I would have changed all the plugs, not just one.

As far as the fuel pump pressure, did they follow that service bulletin I posted a link to in your other post on that problem?
If so, they should have read the last part. Here it is again.

In-Water Test
1. With a vacuum gauge and a fuel pressure gauge in place, operate the boat throughout the RPM range and record the pressure and vacuum readings.
2. If the fuel the supply vacuum reading is greater than 2 in. Hg (7 kPa) , find and correct the fuel supply restriction.
3. If the fuel supply vacuum is within specification and the fuel pressure is less than 40 psi (276 kPa), replace the Cool Fuel Module.
IMPORTANT: It will be necessary to sea-trial the boat following repairs to be sure that the pressure and the fuel system vacuum remain within specification throughout the RPM range.

 

[Mike250]

Re: Spark Plugs

Don, that's exactly what I pointed out to the mechanic. IT"S OUT OF SPEC! His reply was "it's not the problem and will not be covered under warrenty". I plan on calling the warrenty provider which is a company that Cobalt uses for their extended warrenty.

I have a feeling that as long as the engine is running fine their not going to touch the high pressure pump and regultor.

Thanks to all for the input. I did replace ALL the plugs at $100+ but it's worth it in the long run. I'm bringing it home tomorrow and running it on the muffs to make sure it's running smooth.

 

[a70eliminator]

Re: Spark Plugs

Ayuh,... That I Agree with,....



And That,.. I Don't Agree with...

If 38/40psi was Alright,... That's what it would be spec'ed at....

About the plug fouling issue, overly rich mixture, oil past valve guides, weak ignition, whatever, I always thought once that condition is remedied the plugs would burn off all that oil carbon whatever and clean up just by running the engine once tuned right. You guys are saying once a plug gets fouled it's junk,, if the condition is caused by something wrong with the plug itself like worn electrode or wrong heat range then I would have to agree, could you explain what it is that renders a fouled plug junk, I mean you can foul a brand new set of plugs if your engine has any of those problems.???

 

[Mike250]

Re: Spark Plugs

I brought the boat home and fired it up. Runs great at idle.

While I was trying to find the problem last fall I pulled all the plugs and inspected. All looked the same, clean, no deposits etc. I cleaned/gaped the plugs and still had the rough idle problem. I have to say that my cleaning method was a wire brush and carb cleaner that seemed to work well in the distant past. Anyway, from now on I'll be replacing plugs when I suspect one might be fouled.

As far as the low fuel pressure, it was a no-go on replacement under warrenty. I plan on installing the pressure gage and running the engine through the RPM range on my first outing. Based on the results I'll repair it myself if needed.

Again, thanks to all for the input. These forums are a huge help.