Merc head gasket help!!

[jettech]

Hello everyone, I'm new to the site and need some quick help.. I have a 01 Mercruiser V6 that over heated and blew the head gasket on the starboard side. Replaced the head gaskets and had the heads redone by machine shop. Had all the necessary parts replaced along with new wp. Ran the boat on the hose for 15 min. to set timing. Everything is good. 1 week later tried to start engine and it was locked up. Pulled plugs and cylinders were full of water.. Drained water and cranked engine to drain rest of water. Replaced plugs and started engine. It runs but chokes a bit.. Now the only thing that I can think of is the over heating reached a high enough temp to crack the risers or manifold inside to allow water to seep into the exhaust ports and fill the cylinders. What do you guys think the next step should be.. I appreciate all your help.. Thanks

 

[Bondo]

Re: Merc head gasket help!!

What do you guys think the next step should be..

Ayuh,... Pull the manifolds,+ risers to inspect them...

Up in the Adults Only sticky in this forum, You can find links to the Factory Manuals, if that'll Help...

Btw,.. Welcome Aboard...

 

[TilliamWe]

Re: Merc head gasket help!!

jettech, the number one through about number 5 reason for water in the cylinders of a marine engine is a failure of the exhaust manifold(s).
You'll need to replace at least one of your exhaust manifolds.

 

[jettech]

Re: Merc head gasket help!!

I had a thought about the manifolds also but I'm not sure what to look for when I pull them off. I was told that the smallest hair-line crack could leak enough water to flood the cylinders and would not be able to be seen with the eye. The only way to find out there is a leak is to pressure test each manifold. I don't even know if there is a tool to do this with.. Any thoughts.. Thanks again.

 

[TilliamWe]

Re: Merc head gasket help!!

You look for rust on the inside. Or when you take them off you find a bunch of rust scale that just crumbles and falls out.
You don't say where you are or what type of water is around, but at 8 years old, you manifolds were on borrowed time. Regardless of what you "see or don't see" you most likely have one that's bad, and one that is sure to follow.

 

[jettech]

Re: Merc head gasket help!!

Pulled the manifolds and there is not a large amount of rust. Some small particles towards the rubber bellow side of the manifold. This engine has the one peice manifold/riser set up. Now I did notice that the baffles inside the y-pipe were missing. I was told by a tech at the local dealer that the baffles were located near the bellows and not at the transom end. I don't know if this were a problem or not. The boat has only been ran on a hose since the rebuild. Now I could replace both the manifolds like you said just to be on the safe side but they are no longer available from mercruiser. But I found a 2-piece replacement for over a $1000. Any other ideas on what this could be before I start shelling out money???

 

[JustJason]

Re: Merc head gasket help!!

the machine shop could have possibly taken to much material off the heads throwing off the geometery of how the intake manifold fits the head. Pull the intake and see if there is any evidence of water tracing on the intake manifold gasket.

 

[TilliamWe]

Re: Merc head gasket help!!

Those baffles are actually called "exhaust shutters", but most people call them "flappers". They can be important, but they would not be the culprit if all you have done is run it on the hose since. They only come into play when the boat is in the water, and they have to stop water from being forced up the exhaust pipes.
Okay, not a lot of rust in the batwings water passages, but did you see any rust in the exhaust passages? And what about rust at the exhaust ports on the head?
Checking the intake is a good idea too.

By chance, did you actually see the "blown headgasket"?

 

[jettech]

Re: Merc head gasket help!!

No sign of any rust at the exhaust port on the head and manifold. Only signs of rust are at the end of manifold where flappers are located. The heads were done by a professional machine shop that I've never had problems with before but I guess they could have done this one wrong.. I would like to save pulling the heads off for a last option. I did see the head gasket and cylinder 1 and 3 had gasket failure. Whats next??

 

[180shabah]

Re: Merc head gasket help!!

Leakdown test the engine. Then you'll know if it is the engine or the exhaust.

 

[TilliamWe]

Re: Merc head gasket help!!

Leakdown test the engine. Then you'll know if it is the engine or the exhaust.

Yep.

 

[jettech]

Re: Merc head gasket help!!

Any chance someone could tell me were to find the proper procedure to do a leak down test.. Searched the forum but didn't find much on it.. Thanks

 

[180shabah]

Re: Merc head gasket help!!

When you get a leakdown tester, it will come with instructions. But basically you you pressurize a cylinder and watch the gauge for leakage.

 

[chiefalen]

Re: Merc head gasket help!!

Why did it overheat in the first place?

Did you ever discover the cause?

 

[jettech]

Re: Merc head gasket help!!

OK I'll get that purchased and go that route.. I'll let you know what I come up with...

Overheat was caused by an impeller failure and the person driving the boat was not experienced and did not notice it quick enough..