Pulled her, have a project to work on….

aero3113

Is there an easy way to check if it’s a manifold gasket or intake gasket leak? Either would put water in the oil. And could decrease the RPM’s. Would be a lot easier than a head gasket.

PickleRick

You've gotta pull the intake to remove the heads...id pop it off and hope to find a deteriorated gasket between the coolant passage and the bottom of the valley pan gasket. 


I was thinking intake coolant leaks were somewhat common on the vortec 350 due to combo of plastic/composite gasket in automotive application.  Im unsure if the marine engines got a better set up.

I think it would have to be a relaly bad intake leak to hurt the power.  A head gasket in my experience usually hurts power, and you'll find a clean plug where its getting into a cylinder.   Could also find coolant hoses hard as a rock while running if compression is getting into the coolant system.   Needs to get a little warm for the coolant system to start building excess presssue. 

aero3113

What has me confused is that the engine runs really well. Besides the slight vibration when I first started it and then cleared. I would think if it was a head gasket I would at least get a vibration at idle. 

aero3113

@PickleRick , would that allow water into a cylinder though? I want to say it’s definitely getting water into a cylinder by the way the starter acted.

PickleRick

If its a bad enough leak.  My most recent headgasket repairs have been on Rover  4.0/4.6 engines which are simple buick v8s.   The exghaust runners are right next to the coolant passage. Depending on how long the leak has going you could even find pitting on the mating surfaces.   Unelss youre able to see an external leak its hard to say without a tear down.  

I dont know where the coolant passages are in your 5.7, but if you find the clean plug and its a cylinder next to that passage your luck is good.  

Did a quick google seach to see a picture.  The coolant passages in heads will be next to the front and rear cylinders and the intake gasket could spill into the exhaust. 

Cant really look at boat exhaust to see moisture can we??

aero3113

Here’s pictures of when I had the intake off last year.

PickleRick

If you have a clean plug in 1, 2, 7 or 8 luck is in your favor.  

That's unfortunate a big gap between the exhaust and coolant passage.  If it's blown out there it should be very apparent.

Formulaben

Dude, that suuucks!  Hopefully it goes smoothly. 

aero3113

If I narrow it down to an intake gasket, I can replace them while the boat is in the water? I don’t have sea cocks for the water intakes but if I drain some water out of the block it should go down to the water line right?

PickleRick

So long as the intake is above the water line.  If its not it wouldn't be hard to find a plug for the water hose in the hardware store plumbing department.  

I use my  pneumatic powered extractor to suck the excess coolant from the heads once the intake is off.  If the heads must come off i do the same. I always end up with coolant and oil in the cylinders and holes for head bolts.  

I've not seen your boat in person but from pics it looks like you could do intake and heads without removing the block from the hull.  Some boats the engines are so close together you cant fit a pencil between them. 

aero3113

Yes, intake is above the water line and I have plenty of room to do the work with the engine installed. I do have a wooden plug if needed, but that wouldn’t prevent the water from coming in through the exhaust. I’ve replaced the manifolds and risers in the water so I don’t think it will be an issue. I’m hoping I get lucky and I’ll just have to remove the intake. I ordered a full head gasket kit, this way I’ll have everything I need. It seemed like the engine cranked fine but got caught with water in one cylinder (Hopefully 1, 2, 7 or 8). If it was 2 or more cylinders, I think I would’ve had a harder time starting the engine.

PickleRick

Its been a long time since i messed with a Chevy but i was thinking the felpro was the go to intake gasket brand over that of OEM which was prone to failure.  

Just for kicks, before tear down do a compression test while you have all the plugs out. 

aero3113

Yes, I ordered Felpro.
Worried about do compression test because I’ll be pushing more water in.

PickleRick

While the plugs are out any water would push right back out the spark plug hole.  Id probably worry more about moisture getting into my compression gauge.

I'm most interested in the readings of the cylinder that has water intrusion.  

It might be a little lower due to the oil being washed off the rings.   If its substantial, head gasket or possible exhaust valve is stuck open.

Im hoping your numbers read perfectly so you feel much more confident simply replacing the intake gasket.  

aero3113

Picked up some cheap oil and filters to use as a flush.

YYZRC

Do you think the folks at “Super Tech” would be upset learning that they are selling throw away oil and filters? It would be hard for me to go to work everyday knowing customers have zero respect for my product!

aero3113

That’s funny @YYZRC ! 😂

aero3113

So I have water in 1, 3, 5 and 7. Thinking manifold or riser gasket. What do you guys think? Risers and manifolds were replaced in the fall so hopefully not needed. 2, 4, 6 and 8 were all dry and looked good. Starting to pull apart now.

captkevin

hopefully just a gasket. Can't believe new manifolds could be bad. Crazy how rusted the 1st plug is. Good Luck 

aero3113

Yes, that’s # 7 at the the back of the engine where the water pools.

aero3113

I don’t see any smoking guns. Used a borescope and don’t see any visible cracks. Gaskets looked good. I might just go ahead and replace manifold and risers on that side to be safe.

aero3113

Scratch that, found something. Will update soon.

Dream_Inn

aero3113 said:

Scratch that, found something. Will update soon.

Waiting patiently....

PickleRick

We're hoping for good news

aero3113

Head gasket!! Worst was between 3 & 5. I dropped the head off at the machine shop to get checked. I had water in 1 & 7 also. He said that the other cylinders could’ve been leaking even though they don’t show burnt in between like 3 & 5. Also, the water could go into the manifold and back into all the cylinders. Hopefully have the head back by tomorrow or Thursday.

captkevin

crazy that it was bad so soon after replacing

aero3113

I did have the overheat trying to avoid that boat so I’m guessing that caused it to fail. 

aero3113

I’m curious if the head checks out good. What has me questioning is that there was water in all the cylinders on that side.

aero3113

But the boat ran pretty smooth besides the loss of some power.

PickleRick

That really sucks but at least you shouldn't have much downtime