Exhaust Manifold / Riser Issue

[HT32BSX115]

Re: Exhaust Manifold / Riser Issue

I only pressure tested the manifolds. I bolted a 1/2" thick steel plate with a gasket to the top of the manifold using the 4 bolt holes. I then connected my regulated air line to the bottom of the manifolds, with a rubber hose and hose clamps.

Ok. You verified that the manifolds don't leak.

You didn't verify that the risers and/or riser gaskets didn't leak. (which is one of the most common reasons (other than wash/splash-back) for liquid water in the exhaust ports.

 

[300sflyer]

Re: Exhaust Manifold / Riser Issue

Ok. You verified that the manifolds don't leak.

You didn't verify that the risers and/or riser gaskets didn't leak. (which is one of the most common reasons (other than wash/splash-back) for liquid water in the exhaust ports.

All 4 riser gaskets, [OEM Quicksilver gaskets] were in perfect condition. In fact both the manifolds and risers look almost new. There was no evidence of any leakage at the joint. How does one pressure test the riser itself?

 

[HT32BSX115]

Re: Exhaust Manifold / Riser Issue

All 4 riser gaskets, [OEM Quicksilver gaskets] How does one pressure test the riser itself?

It's not possible to "pressure" check them easily.

There is a way to block the bottom using the plates you made for the manifolds. Fill them (standing upright) with acetone and see if acetone seeps into the exhaust area. Acetone will seep through cracks/leaks that water won't readily seep through quickly.

Other than that, you have to look at the shutters and (lack of) riser extensions, Or, if someone shut both engines down while under way.


The other possibility is head cracks, There's only a few places water can get into the exhaust area. I would still suspect riser gaskets. But if they're leaking you would (or should) see rust trails below the gaskets... and NO rust above the gaskets (in the riser)

By the way, If these are salt/raw water cooled engines, and you do not know how old the manifolds/risers are and there's considerable rust inside them, now would be a good time to replace them. A leaking manifold or riser can destroy an engine in a rather short period of time.

 

[300sflyer]

Re: Exhaust Manifold / Riser Issue

It's not possible to "pressure" check them easily.

There is a way to block the bottom using the plates you made for the manifolds. Fill them (standing upright) with acetone and see if acetone seeps into the exhaust area. Acetone will seep through cracks/leaks that water won't readily seep through quickly.

Other than that, you have to look at the shutters and (lack of) riser extensions, Or, if someone shut both engines down while under way.


The other possibility is head cracks, There's only a few places water can get into the exhaust area. I would still suspect riser gaskets. But if they're leaking you would (or should) see rust trails below the gaskets... and NO rust above the gaskets (in the riser)

By the way, If these are salt/raw water cooled engines, and you do not know how old the manifolds/risers are and there's considerable rust inside them, now would be a good time to replace them. A leaking manifold or riser can destroy an engine in a rather short period of time.

Thanks for all the info. The boat is in fresh water, and like I said, the manifolds and risers look almost new both inside and out. Shutters in the Y-pipes are all in good shape as well. I had a small amount of water in all 4 manifolds, and I would be very surprised if all 4 heads had cracks in them. When I changed the oil in both engines, there was no trace of any water in the used oil. [about 40 hrs running time]

I can only conclude one of two things has happened.

1- The engines idled for almost an hour during the oil change, and this allowed water to enter the manifolds due to "reversion".

2- The tipping point in the risers is too close to the waterline when the boat is fully loaded, and I need to ad riser extensions.

 

[HT32BSX115]

Re: Exhaust Manifold / Riser Issue

I can only conclude one of two things has happened.

1- The engines idled for almost an hour during the oil change, and this allowed water to enter the manifolds due to "reversion".

2- The tipping point in the risers is too close to the waterline when the boat is fully loaded, and I need to ad riser extensions.

That is possible.

I have 3" riser extensions on my 454. If I could put 6" extensions on it I would....More is better.

Here's a great article on reversion.

http://www.lightningheaders.com/tech-info(2).htm

Cheers,


Rick

 

[300sflyer]

Re: Exhaust Manifold / Riser Issue

That is possible.

I have 3" riser extensions on my 454. If I could put 6" extensions on it I would....More is better.

Here's a great article on reversion.

http://www.lightningheaders.com/tech-info(2).htm

Cheers,


Rick

Interesting article!

When adding riser blocks, do you need to change the elbows as well? Can't see how everything would line up with the riser sitting 3" higher.

 

[HT32BSX115]

Re: Exhaust Manifold / Riser Issue

Interesting article!

When adding riser blocks, do you need to change the elbows as well? Can't see how everything would line up with the riser sitting 3" higher.

You usually use the same elbows. The connections obviously have to be altered to make it all fit.

 

[300sflyer]

Re: Exhaust Manifold / Riser Issue

After looking at at everything very closely, I have decided to add 3" extensions to both my engines. They will fit under my hatches.

So, it is now obvious to me that I need 4 new elbows [Merc # 14801-C] that connect to the Y-pipe, or I have to find longer rubber exhaust hoses, to go between the current elbows and the Y-pipe. If I can find longer exhaust hoses, this would be much simpler and less expensive as well. Those extended elbows are about $400 a pair! Which method seems to be the exceptable way of doing this?

 

[81 Checkmate]

Re: Exhaust Manifold / Riser Issue

Longer hose! Would be my method

 

[300sflyer]

Re: Exhaust Manifold / Riser Issue

Another thought on where the water might have come from:

I was noticing the tailpipe on my wifes car [Chevy V6] as the engine warmed on a cool morning this past week, and what do I see coming out of it.... WATER, and a fair amount of it! I had completely forgot that one of the by-products of an internal combustion engine, is H2O.

Could the H2O produced by the engine, have condensed on the cool exhaust manifolds, and this is what I saw?

Just a thought... I'm still going to install the 3" riser spacers anyway.

 

[jze1212]

Re: Exhaust Manifold / Riser Issue

If you are not seeing any rust . . . and the amount of water is small . . . then I vote for condensation. That is why we fog engines for the winter layup.

I'm with tpenfield on this one..

 

[Glaspar_Fan]

Re: Exhaust Manifold / Riser Issue

Another thought on where the water might have come from:

I was noticing the tailpipe on my wifes car [Chevy V6] as the engine warmed on a cool morning this past week, and what do I see coming out of it.... WATER, and a fair amount of it! I had completely forgot that one of the by-products of an internal combustion engine, is H2O.

Could the H2O produced by the engine, have condensed on the cool exhaust manifolds, and this is what I saw?

Just a thought... I'm still going to install the 3" riser spacers anyway.

Definitely a possibility, and the more likely if the engines were only run for 5-10 minutes.

How are you shutting the engines down? An old Chrysler manual I had said to run the engines up to around 2K rpm, then slowly bring them back to an idle and promptly shut off the ignition. (Point being to minimize the chance of sucking water back in through the exhaust.)

John

 

[300sflyer]

Re: Exhaust Manifold / Riser Issue

Definitely a possibility, and the more likely if the engines were only run for 5-10 minutes.

How are you shutting the engines down? An old Chrysler manual I had said to run the engines up to around 2K rpm, then slowly bring them back to an idle and promptly shut off the ignition. (Point being to minimize the chance of sucking water back in through the exhaust.)


John

The engines ran for about 40 min in total, during the oil changes, and to haul the boat on a travel lift. The only time they went above idle, was at startup.