exhaust manifold failure, how did you know?

[dogfish1]

Hi all, I am new to inboard engines and the manifolds sound like a common failure. Looking into replacing the manifolds and risers and I think I will be into it for over $1200, plus a day in the bilge. Boat is an '03 with twin 5.0MPI's and Bravo drives. Seems like a lot of money to waist if the manifolds are good, also seems like a small amount of money compared to putting water into the engines and causing them damage.
So for those of you unfortunate enough to have a failure how did you know? I imagine if they crack on the outside it would be easy to tell but if they just wore away on the inside is your first signal when the engine starts miss firing or when you find water in the oil, or ??????

 

[Bondo]

Re: exhaust manifold failure, how did you know?

Ayuh,... Welcome Aboard,.... The most common failure point is where the manifold, 'n riser meet...

Ya can pull the risers, inspect the gaskets, 'n the gasket sealin' surfaces...

If the gasket sealin' surfaces are gettin' thin, replace 'em...
otherwise, replace the gaskets, 'n check 'em again next year, or the next...

 

[tpenfield]

Re: exhaust manifold failure, how did you know?

Usually they just wear away on the inside. More the issue in salt water than fresh water. Rust around the joint between manifold and elbow or riser can indicate an issue.

as Bond-o said, inspection, probably on 3-5 year intervals, would indicate if the mating surfaces are getting too thin.

 

[Fishermark]

Re: exhaust manifold failure, how did you know?

You might want to know what kind of exhaust you have before you start pulling the risers. Being an '03 you might have dry exhaust. I don't know what engines they used them on.... but the gaskets are expensive and it is probably unnecessary to pull them. IF they are dry exhaust. Just something to check.

 

[Don S]

Re: exhaust manifold failure, how did you know?

Do you boat in saltwater? If not, then you probably don't need new manifolds or risers.

 

[dogfish1]

Re: exhaust manifold failure, how did you know?

I didn't realize that they made dry exhaust for boats with exhaust that goes out through outdrives? I keep my boat in a river about 1 1/2 miles north of the Long Island sound. Most of the time the engines and exhaust end their day in brackish water.

 

[Bondo]

Re: exhaust manifold failure, how did you know?

I didn't realize that they made dry exhaust for boats with exhaust that goes out through outdrives? I keep my boat in a river about 1 1/2 miles north of the Long Island sound. Most of the time the engines and exhaust end their day in brackish water.

Ayuh,... It's Not dry exhaust, it's dry joint manifolds,....

Big BIG difference....

 

[Fishermark]

Re: exhaust manifold failure, how did you know?

Ayuh,... It's Not dry exhaust, it's dry joint manifolds,....

Big BIG difference....

Good point. Yes, I should have said dry joint manifolds.

 

[dogfish1]

Re: exhaust manifold failure, how did you know?

Ayuh,... It's Not dry exhaust, it's dry joint manifolds,....

Big BIG difference....

Can you tell just by looking at them or do I need the serial number from the engines? It seems like the serial numbers are critical for so many parts.

 

[OllieC]

Re: exhaust manifold failure, how did you know?

Dry joint has separate chambers for water outside the the exhaust (see the round sections where they mate below)


The other looks like this. The water chambers run along side the exhaust. (see below the small ports on the gasket)


I will probably be corrected on my terminology.