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So i know its not a car, but its almost a car motor right? ;) Anyways, i got this boat and the previous owner said it overheated really bad, then once it cooled down he could not get it to start again. First guess was head gasket or cracked head? About 10 minutes into it i found a greyish milky color oil on top of the cylinder heads, but not in the oil pan. The majority or the milky grey oil was right around the studs on the head for the rocker arms.. Is there any obvious thing that would be wrong with this that i'm not seeing? I've seen cars where they had full oil pans of just milky grey oil, but this one just has a slight build up around the rocker studs. The other thing i noticed is the pushrods had a slight amount of rust/grey buildup at the top 1/2" of them. I was thinking maybe the valve covers leaked and water got in there or something but they look like they sealed well. Anyone have any ideas if this is something weird or just a simple head gasket change?
 

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It`s not uncommon for condensation to get in the engine and it`s going to make it`s way to the highest point in the engine which is the valve train and valve covers. I would say this is especially true on a engine that is cooled by cold water. Since the engine won`t run I would do the usual checks, spark, fuel, etc. I would also give it a compression check on each cylinder. I`ve seen in a couple of cases where they were run so hot detonation set in and chipped up the piston top or caused a piece of the piston to break away. In most cases when they are run excessively hot the ring seal is gone due to excessive expansion. A compression check should also tell you if it has a cracked head or blown head gaskets.
 

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Blackhauk90 said:
The majority or the milky grey oil was right around the studs on the head for the rocker arms. The other thing i noticed is the pushrods had a slight amount of rust/grey buildup at the top 1/2" of them.
This should be a dead give-away that whomever put the heads together failed to use a sealer on the rocker stud threads where they screw into the head. See the bottom diagram here to see that the stud screws directly into the water jacket.
http://www.iskycams.com/holesawing.php
 
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