wet exhaust set up

[Marty Levenson]

Hey All,

Started getting ready to take my old A4 out of the boat. I believe I have an unusual hot water to exhaust set up, and I'm wondering if I should keep that or change it when I install my rebuilt A4.

The (black pipe) gas exits the exhaust manifold, goes straight up about two feet, comes back down, and leads into a muffler. The (hose) hot water exits the exhaust manifold, goes up about a foot, and joins the exhaust gases as it enters the muffler. In other words, the water does not enter the exhaust pipe before the riser, as I see in many photos on this site, but after. The riser did get quite hot cruising on a hot day, so i have an insulating jacket around it. Attached photo shows a bit of the set-up, and the heat jacket. You can see the hot water hose going aft of the exhaust riser. I'll take some better pictures this week. Any thoughts if I should change it to the conventional set up or leave it be? The current system did work well.

Thanks!
Marty

[Marian Claire]

I believe what you have is correct. My wet/dry connection is on the down side of the dry loop. If you introduced the water on the up part it could/would run right back to the manifold and cause bad things to happen. Do you have the water lift type of muffler? You may have seen pics of the standpipe type which is plumbed differently. Dan S/V Marian Claire

[Carl-T705]

Very Very nice job on the insulation cover/wrap!!

[Marty Levenson]

Thank you for the replies.

No, not the waterlift type of muffler.

The insulation wrap was a local Vancouver company that builds custom marine wraps...about $100. I just supplied a drawing by e-mail and they had it ready a couple days later. Installation not included. I thought it was a great deal, easy to install.

Guess I'll leave well enough alone when I install the new A4!

Thanks again.

[chiron]

This is off the subject but what is that gold colored cylinder on top of the transmission on Marian Claire's engine?

[jpian0923]

A really big coil?

[Marian Claire]

Oil filter. Dan S/V Marian Claire

[lat 64]

That oil filter looks identical to the one on my '61 chev pick up. A Fram aftermarket unit. Can you still get cartridges for it?

[Marian Claire]

I forget the NAPA # but the Fram C-4 filter fits. They, NAPA, Autozone etc, can get them in a day or two so I stock up before a long trip. Dan S/V Marian Claire

[Carl-T705]

Did the wrap get rid of the heat build up?

[Marty Levenson]

It seemed to contain it: the deck above that pipe used to get quite warm, but not after installing "the wrap".

-Marty

[ILikeRust]

The (black pipe) gas exits the exhaust manifold, goes straight up about two feet, comes back down, and leads into a muffler. The (hose) hot water exits the exhaust manifold, goes up about a foot, and joins the exhaust gases as it enters the muffler. In other words, the water does not enter the exhaust pipe before the riser, as I see in many photos on this site, but after.

Any thoughts if I should change it to the conventional set up or leave it be?

Maybe I'm just confused here, but your description to me sounds like the "conventional setup". Where have you seen photos of the water entering the exhaust before the riser? That seems to me to be a recipe for disaster.

If I am understanding your description correctly, it sounds to me like you have the standard "hot section", with the water injection coming just before the muffler. If you don't have a water lift muffler, what do you have?

[edwardc]

... Where have you seen photos of the water entering the exhaust before the riser? That seems to me to be a recipe for disaster.

I think what he may be describing is a jacketed elbow, where the water circulates through an outer shell surronding the exhaust elbow, and finally mixes with the exhaust after the riser, through an internal opening.

As I'm sure you know, these are prone to a failure mode where the internal exhaust pipe rots out and lets water into the manifold. Not my choice.

[Marty Levenson]

Thanks for the replies. I was initially confused: my set-up is the conventional one. The hot water exists the exhaust manifold and then enters the muffler after the "hot section".

[JOHN COOKSON]

Marty
If your current exhaust works well and you are happy with it leave it alone.

Having said that here are a few ideas for your consideration:

When you put everything back together cross plumb the manifold so water enters at the low end and goes out at the high end of the water passage. This will eliminate possible voids\air pockets & hot spots.

If it has been a few years since the riser has been inspected, while the engine is out and access is easy, remove the wrap and check for thin spots. The wear will be from the inside out because of the hot gasses. Grabbing the pipe and torqueing it around will help find any thin areas. Another problem area is where the water is injected if there is any metal in the area. If there is a bronze injector part in an iron pipe this area degenerates rather quickly.

If the riser is a bit on the hot side you can always add another layer of wrap. I have two layers of fiberglass wrap on my riser. When everything gets good and hot I can put my hand on it for a few seconds and not get burned.

Happy wrenching.

TRUE GRIT

[Marty Levenson]

Thanks Grit,

That sounds like a plan. I want to head off as many future problems as possible.

-Marty

[Laker]

Dan - Forgive me for straying a bit , but could you help me understand the plumbing/routing at the point of water discharge atop your manifold? I am unfamiliar with the arrangement you show a couple of posts back.

Thanks , CJK

[sastanley]

Marty, I have a question. When the water exits the manifold, does it rise above the waterline to a siphon break before it comes back down and is injected into the backside of the 'hot section'? :confused: This is important to avoid siphoning water back in to the hot section (and subsequently dumping into the cylinders) when the engine is not running.

I'll +1 that cool heat jacket. I wish I could do something like that where the exhaust goes by my ice box. :rolleyes:

[Kelly]

CJK,

I have a similar setup on my engine. The "T" on the manifold discharge has a water temperature sensor screwed into the starboard side while the port side feeds a Dole thermostat housing. There are two exits from the thermostat housing: one heading aft to the hot exhaust injection point just upstream from the muffler (you can see a red-handled valve in this line) and one heading forward- back toward the engine cooling circuit. How much water is directed overboard or back into the circuit is controlled by the thermostat.

Dan seems to have the bypass loop (forward) plugged but I can't be sure in the photo.

[Laker]

That makes sense , but a question : does that set-up take the place of the thermostat which is contained in a turtle-looking casting which is on top of the head on the flywheel on 70's models such as mine? M.C. has an early A-4 , based on the tranny cover.

[Kelly]

The Dole thermostat can replace the thermostat in the head (turtle) but the functioning is not quite the same. In a raw water cooling system, the Dole will vary the amount of water being sent to the muffler, thereby resulting in varying exhaust temperatures. In my setup, this makes the exhaust get too hot.

The in-head thermostat ensures full flow to the exhaust at all times.

This difference is not an issue in fresh water cooling circuits as the thermostat is only controlling the volume of fresh water either passing through the heat exchanger or bypassing it.

[ndutton]

One of the best I've seen in a while; brief, to the point and dead on.

[Laker]

That makes sense , Thanks Kelly. CJK

[Marty Levenson]

Marty, I have a question. When the water exits the manifold, does it rise above the waterline to a siphon break before it comes back down and is injected into the backside of the 'hot section'? :confused: This is important to avoid siphoning water back in to the hot section (and subsequently dumping into the cylinders) when the engine is not running.

I'll +1 that cool heat jacket. I wish I could do something like that where the exhaust goes by my ice box. :rolleyes:

The water exit hose does go up in an arc about 16" above the top of the exhaust manifold, and then down to where it enters the muffler. Never thought about whether that was above the waterline (!). Its never been a problem: been exactly like this since 1967. The problem you suggest makes sense: maybe I'll make that run a little higher when I reinstall!

Glad you like my cool jacket!

-Marty

[sastanley]

OK Marty, good deal..mine is about the same on my C-30. I am limited by the height of the counter top, since the engine sits in the middle of the boat. The hose exits the manifold, heads up into the counter top structure near the sink, and comes back down to the mixing elbow.

It just wasn't obvious in your picture so I wanted to double check. ;)

[Marty Levenson]

....appreciate any feedback or "hey wait a minute!"'s...

I know how much I don't know!

-Marty

[ILikeRust]

Known unknowns are certainly better than unknown unknowns.

[Marian Claire]

Laker: Post 17? I have used many cooling set ups on the MC. In the pics in question I am not using a T-stat so the Dole housing is simple a T. One side is blocked and the other, with red valve, goes to the wet/dry connection. I regulated temp by restricting the flow. I later changed to the recirculating loop that can be seen in some of my album pics. Now I have canged to FWC. I still do not use a T-stat and have a recirculating loop in the fresh part that bypasses the HX. Sorry for the late reply. Dan S/V Marian Claire

[Administrator]

Known unknowns are certainly better than unknown unknowns.


Bill T., we used to talk about "conscious incompetence" versus "unconscious incompetence."

Same sort of thing, I guess.

Bill

[Laker]

M C --- So , basically , what you have is a pilot controlled manual t-stat. Is that about correct?

[Marian Claire]

Thats a good way to discribe it. Dan S/V Marian Claire