www.iFourWinns.com

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?

I'll answer my own question.

Oh dear.

Blown head gasket, cracked head or intake, leaky intake gasket, or bad exhaust

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Let's hope it's not all of them!

Let's start with these questions:
How was this engine winterized?
Was it overheated?

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

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.

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....

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

I was all ready to change the oil before this happened - it's a good job I didn't! Thanks for your replies.

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.

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

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.

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

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II