I just installed a used stainless marine exhaust(pressure tested before install) with long risers on my boat. I immediately got a small amount of water bubbling out of the vband(manifold to riser joint). I tightened the v band up alittle and got less bubbling but still a small amount. Is it safe to say there shouldn't even be water at that joint?

No...those should be dry joints. You have a gasket on the joint surface?
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Maybe it's leaking at a weld joint by the flange?

Bubbling typically doesn't mean things.

You said immediately, before it even warmed up?

yes I have a gasket there.

i guess immediately wasn’t the right choice of words, the boat was running for 10 mins or so. I was up to 140-150* water tem, Before I noticed it

I’m going to run jt again tonight and report back

Yep - dry joint.

Are you sure your hoses are tight? A dribble could bubble due to heat at the joint.

Did you use any sealant at the joint? Most would say to get rid of the gasket and just use high-temp rtv.

Most likely reversion, which could be caused by a leaky riser connection. Be sure the gasket is in good shape, along with using some good hi temp gasket sealer.

Great idea, thanks guys. I’m gonna take it back apart and add some high temp RTV

can you please explain this more, how does a bad riser connection cause reversion?

The water leaves the manifold through the rubber external 90* hose and enters the riser through said hose. And then travels down the riser where it exits the water jacket some inches before that back of the boat. Is this correct? So in theory there should be no water anywhere near that joint.

Assuming raw water cooled Stainless Marine exh manifolds, operating temps could create a scenario where a small crack may have held your pressure test, but not the higher then tested pressure/heat. Something like that.

I don't know enough about it to explain it in detail. Just using past personal experiance with reversion issues over the years.

Pour a cup of coffee and search this site for "stainless marine exhaust reversion".

You will learn more than you want to know!!

Steve

Is this a wet or dry exhaust?

wet is what you explained…water dumps a few inches from the end and mixes with exhaust. If that’s the case it could be reversion. But you would need a lot to see it bubbling at the joint.

I don’t see how dry exhaust would cause reversion.

you could have a pin hole leak either in the manifold, riser, or tail that’s causing the water leak. Would need to do a pressure test to eliminate all possible leak paths.