Odd Plug after 10hours of USE (photo)

[dsinger]

What cause this plug to look like this? The motor runs fine but at idea sometimes it acts like it is missing a cylinder. I say it runs fine I have lost some RPMS at WOT.

 

[rickdb1boat]

Re: Odd Plug after 10hours of USE (photo)

Looks to me like you're getting some water in that cylinder. I'd do a compression test...

 

[dsinger]

Re: Odd Plug after 10hours of USE (photo)

I checked it and it was still at 120 on all four

 

[RPJS]

Re: Odd Plug after 10hours of USE (photo)

Your getting water in the cylinder with the clean plug, the plug is being constantly steam cleaned.
The first suspect would have to be the head gasket

 

[dsinger]

Re: Odd Plug after 10hours of USE (photo)

I need to pull the head and look I guess.

 

[dsinger]

Re: Odd Plug after 10hours of USE (photo)

I will go pull it be back in 10 min

 

[rickdb1boat]

Re: Odd Plug after 10hours of USE (photo)

That would be a good idea at this point. Compression should reveal a problem...

 

[DJ]

Re: Odd Plug after 10hours of USE (photo)

I'm not sure which engine this is. If it's a cross flow V-4, don't expect to see signs of an obvious leak.

I've had more than one that washed down plugs (particularly #1) and could see no signs of the head gasket leaking. However, a new gasket fixed them.

Go figure.

If you replace the head gaskets, don't forget to re-torque after one heat up/cool down cycle.

 

[BoatBuoy]

Re: Odd Plug after 10hours of USE (photo)

That's what I was going to say. It looks to me like that plug hasn't fired since you put it in.

 

[dsinger]

Re: Odd Plug after 10hours of USE (photo)

Well now that djohns said I wont be able to see any signs I won t do any good to say I did not see any. Let me ask you this I found that the coil has a short or something wrong. It won t spark unless you pull and twist on the plug wire I checked the boot end and it was fine. I used my advanced timing light and found the bad section is in the part where the plug wire goes into the coil pack. What would the plug look like if the cylinder has never sparked since the plug was put in new. Should I replace the coil pack and the gasket or just the pack and see it looks normal after that. I know the gaskets are cheap but I hate to take it apart if it aint broken.

 

[DJ]

Re: Odd Plug after 10hours of USE (photo)

It's difficult to tell from the pic's. but I certainly won't discount the theory that the plug in question isn't firing.

You have the right idea, checking with a timing light.

Just switch one of the other coils to that location and test.

 

[rickdb1boat]

Re: Odd Plug after 10hours of USE (photo)

Yep. If the compression is still good(Which it is), look at firing to be the problem...

 

[dsinger]

Re: Odd Plug after 10hours of USE (photo)

Ok I switch four and two on the pack and it seems the pack is not working because the what I thought was the bad coil will fire when I switch the postion on the pack. Could anything else cause this other than the pack being bad.