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| Spark plug diagnosis https://www.smwebhead.com/phpBB3/viewtopic.php?f=6&t=15392 |
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| Author: | Terrieal [ Fri Apr 14, 2017 6:03 am ] |
| Post subject: | Spark plug diagnosis |
Hi all. I just wonder if any of you have any insight into why one of my spark plugs looks like this:  I think it might be the cause of my lumpy running. I've replaced all of the leads, cap, rotor, plugs. Also new fuel filter. Then I found this. Any ideas please? |
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| Author: | Terrieal [ Fri Apr 14, 2017 9:04 am ] |
| Post subject: | Re: Spark plug diagnosis |
I'll answer my own question.  Oh dear. |
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| Author: | LouC [ Fri Apr 14, 2017 2:03 pm ] |
| Post subject: | Re: Spark plug diagnosis |
Blown head gasket, cracked head or intake, leaky intake gasket, or bad exhaust |
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| Author: | Terrieal [ Fri Apr 14, 2017 2:07 pm ] |
| Post subject: | Re: Spark plug diagnosis |
Let's hope it's not all of them! |
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| Author: | LouC [ Fri Apr 14, 2017 6:43 pm ] |
| Post subject: | Re: Spark plug diagnosis |
Let's start with these questions: How was this engine winterized? Was it overheated? |
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| Author: | Terrieal [ Sun Apr 30, 2017 1:33 pm ] |
| Post subject: | Re: Spark plug diagnosis |
To complete this story, it turns out that I had a rusted manifold which fortunately only dumped a significant amount of water in a couple of cylinders overnight while the boat sat on the pontoon. Lucky escape. No damage done. One replaced so far, which satisfies me that is running ok again. The other is lost somewhere with a courier, but as soon as I get it, it's going on also. The risers are not yet two years old, so I'll keep them for a little while yet. Could those manifolds be the originals? They'd be 17 years old. I have all of the paperwork from day one, and there's no record of replacement. 
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| Author: | LouC [ Sun Apr 30, 2017 4:21 pm ] |
| Post subject: | Re: Spark plug diagnosis |
Ok get it running and get it warm enough to boil out that moisture. Change oil 2-3x till you don't see milk under the valve covers.... |
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| Author: | Terrieal [ Sun Apr 30, 2017 4:42 pm ] |
| Post subject: | Re: Spark plug diagnosis |
I was all ready to change the oil before this happened - it's a good job I didn't! Thanks for your replies. |
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| Author: | LouC [ Sun Apr 30, 2017 6:29 pm ] |
| Post subject: | Re: Spark plug diagnosis |
They look like they could be original. Salt water or fresh? If in salt figure on replacing them between 5-7 years. That joint between the riser and the manifold is where they often leak. If you see rust trails on the outside, it could be leaking inside. |
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| Author: | Terrieal [ Sun May 07, 2017 4:48 am ] |
| Post subject: | Re: Spark plug diagnosis |
To conclude this story, I spent twelve hours(!) yesterday replacing the other manifold. One of the bolts snapped, leaving a quarter inch proud which caused a slight delay! Had to drill it out in the end, luckily only removing a small area of thread which hasn't caused any problem. What a pain that was. All done now though; just need to replace the hose from the pump to that manifold as it's dripping a little. I ache in places I didn't know I had. |
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| Author: | LouC [ Sun May 07, 2017 11:41 am ] |
| Post subject: | Re: Spark plug diagnosis |
Not a fun job, eh? On my '88 4.3 they used nice zinc plated studs and nuts/lockwashers. I have never had a problem getting the manifolds off this engine and I've done it at least 3 times. All salt water use. In my opinion this is the way marine manifolds should be attached to the head. Much much easier. I would spray some silicone on the Y pipe below the rubber exhaust hoses, loosen the clamps, pry the hoses loose and slide them down, and in about 15 min the manifolds (OMC Batwing one piece units) were off! https://www.dropbox.com/s/u3w9g3qvuxycb ... 1.jpg?dl=0 |
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