View Full Version : water in spark plug hole

10-15-2010, 12:25 AM
I discovered the spark plug issue a few weeks ago and just now started tearing into things to figure out the cause. The original thread is here: http://www.mastercraft.com/teamtalk/showthread.php?t=37857&page=3.

I beleive I may have found the culprit (exhaust manifold), however, I want to double check with others to see if I'm interpreting my findings correctly. The boat is a 1994 prostar TBI with 349 hours.

The important background first. Did compression check and vacuum check after finding the water:

-The compression test showed full compression 165 +/- in the cylinder with water

-An adjacent cylinder only showed compression of 140. The cylinders did not seem affect one another so the issues seem unrelated.

I pulled the exhaust manifold and found rust inside of it, especially the area that aligns to cylinder that I had discovered water. I assume this confirms that the manifold is the cause. However, I want to make sure that the water couldn't have getten into the cylinder from the head gasket first and then found it's way to the exhaust manifold?

I'll post pictures in a few.

10-15-2010, 12:58 AM
Here are some pictures of the Exhaust Manifold:

-The first picture aligns to the #2 or front right cylinder.

-The second picture aligns to the #4 cylinder (where I had discovered water in the spark plug hole) and to the #6 cylinder that had no water but only 140 compression (the one on the right in the pic).

-The third shows the back cylinder #8.

10-15-2010, 01:00 AM
Here are pictures of the exhaust valves. The first shows the front valve (#2) for comparasin.

The second picture shows the exhaust valve on the cylinder that had water (#4 on right of picture) and the one that had low compression (#6 on left sid of pic).

10-15-2010, 01:07 AM
I found water sitting on top of the exhaust valve in cylinder #4 wich was no surprise (this is the valve on the right in the last picture). I also found a little water in #8 which had no evidence of water until now.

So my questions.

-I assume I can now be confident that the exhaust manifold is the problem? I just want to be sure that the water came from the exhaust manifold as opposed to from the head gasket, then to the cylinder, then to the manifold through the exhaust valves.

-Should I do anything about the cylinder that had only 140 compression vs 160-170 for all the others?

-Should I somehow clean out the exhaust valves while I've got access? Does the carbon/soot seem more than normal?

Thanks ahead of time!