Copper jacketed exhaust problems

[ForeverDes]

I have an Atomic 4 engine in my sailboat, and all season I was plagued with rough operation and fouled plugs. After checking the coil, cleaning the carb, etc., I tested the exhaust back-pressure, and it was around 5 psi, while Moyer recommends no more than 2 psi.
The problem has persisted since the season began, both before and after I added fresh water cooling.
I brought the boat home last week, and today I was able to take the exhaust off, expecting some blockage, but I found no evidence of any restrictions, in the gas or water chambers.
I'm concerned that water is entering the exhaust prematurely, say through a broken, i.e. freeze crack, between the water and gas chambers. My problem is, I'm not sure how to test the internal integrity. Does anyone have any thoughts on how to go about this?
For more information, I ran a garden hose into the water inlet and it ran through the water chamber and out the end fine, with no evidence of water in the gas pipe. I then ran water through the gas pipe and washed a very small amount of soot out, and the water appeared to run freely both times,
My very old engine has a gear pump style water pump, and it puts out very little pressure.

[Bill O]

Had an A4 motor a long time ago that that seems very long and overly complicated exhaust tube.

As I recall the exhaust tube was black pipe (id 1.25-1-5"?) and a standard elbow fit onto the exhaust manifold. The pipe went up 20-24" straight up (as high as possible in the engine room) with a mixing elbow at the end. The pipe was wrapped w/heat tape.
This was an inexpensive and easy set up that lasted years (in salt water).

[ForeverDes]

Originally Posted by Bill O

Had an A4 motor a long time ago that that seems very long and overly complicated exhaust tube.

As I recall the exhaust tube was black pipe and a standard elbow fit onto the exhaust manifold. The pipe went up 20-24" straight up (as high as possible in the engine room) with a mixing elbow at the end. The pipe was wrapped w/heat tape.
This was an inexpensive and easy set up that last years (in salt water).

Replacing it with black pipe is definitely an option, but I'd have to have a very long hot pipe section before I could rise vertically and introduce cooling water at the high point. My engine sits directly below the cockpit sole, which is itself lower then the outlet on the transom. I have no choice but to travel aft 4 feet or so from the back of the engine before I can make a significant rise.

[Bill O]

The heat tape did reduce some of the heat coming off the dry stack. The blower reduced the heat in the motor box, since it should be on while using the motor.

The A4 I had was under the cockpit also and was able to get it high enough to not be an issue in an old CCA design boat.

[Searles]

Back pressure will cause fouling of the spark plugs ,the larger the I.d of the gas part of the pipe and larger radius bends the better coupled to a larger sized outlet ,back pressure is the enemy in marine exhaust systems .

[ForeverDes]

Originally Posted by Searles

Back pressure will cause fouling of the spark plugs ,the larger the I.d of the gas part of the pipe and larger radius bends the better coupled to a larger sized outlet ,back pressure is the enemy in marine exhaust systems .

It looks like 1 5/8" ID, which is pretty standard for the Atomic 4, from what I have found on the Moyer Marine forums, and the 2 bends aren't particularly tight, either. Add the fact this has apparently worked well for 60 years, until this season, and I doubt the excessive back pressure is caused by a design flaw.

Which is why I'm trying to figure a way to test the integrity of the water jacket. I'm considering there might be water getting into the gas pipe and pooling at the 45 degree bend, which is the lowest part of the system. It's a short, downhill run to the transom, through < 12" of exhaust hose, from where the water *should* be mixing with the gas, at the aft end of the exhaust pipe.

[Searles]

The back pressure maybe in the exhaust manifold or actually at the exhaust ports,not necessary in the pipe ,carboning up is not uncommon in older engines ��⛵️

[ForeverDes]

Originally Posted by Searles

The back pressure maybe in the exhaust manifold or actually at the exhaust ports,not necessary in the pipe ,carboning up is not uncommon in older engines ��⛵️

I put a brand new manifold on this spring, because the original had a hairline fracture, but it wasn't carbon heavy. The exhaust ports were clean as well. The exhaust itself isn't plugged with carbon; water runs freely, and very very little soot washed from it when I ran a hose into it.
Furthermore, with the exhaust off the engine, it runs much more smoothly, leading me to believe the exhaust itself is the problem.

Again, all of this leads me to believe I may be getting water in the gas pipe of the copper-jacketed exhaust, which is why I'm seeking some way to pressurize the water jacket and check for water ingress into the gas pipe, or some other way to verify the integrity of the exhaust.

I realize I may be barking up the wrong tree, but I'd like to verify this particular issue, one way or another, before I start searching for the problem in other, seemingly less likely, places.

[fourlyons]

Ok, if you want to check for integrity between gas and water chambers, plug one end of the water chamber (or gas chamber) and pull a vacuum at the other end of the water chamber (or gas chamber) with a cheap hand vacuum pump that mechanics use to bleed brakes etc. Just don't close off both gas and water at the same time.

If you're in the States, Harbor freight sells one. You can use tape, or plumbers test plugs to close the pipe ends.

[ForeverDes]

Originally Posted by fourlyons

Ok, if you want to check for integrity between gas and water chambers, plug one end of the water chamber (or gas chamber) and pull a vacuum at the other end of the water chamber (or gas chamber) with a cheap hand vacuum pump that mechanics use to bleed brakes etc. Just don't close off both gas and water at the same time.

If you're in the States, Harbor freight sells one. You can use tape, or plumbers test plugs to close the pipe ends.

Thanks, that's a very good idea.

[wsmurdoch]

I have had for three years, bought from Amazon, a "DEPSTECH Wireless Endoscope, IP67 Waterproof WiFi Borescope Inspection 2.0 Megapixels HD Snake Camera for Android and iOS Smartphone, iPhone, iPad, Samsung -Black(11.5FT)". I is a handy thing to have. I don't know your piping, but it or something similar (and newer) might allow you to get your eyes inside the exhaust piping to see if water is getting in somewhere where it should not while you have the pipework off the engine.

[ForeverDes]

Originally Posted by wsmurdoch

I have had for three years, bought from Amazon, a "DEPSTECH Wireless Endoscope, IP67 Waterproof WiFi Borescope Inspection 2.0 Megapixels HD Snake Camera for Android and iOS Smartphone, iPhone, iPad, Samsung -Black(11.5FT)". I is a handy thing to have. I don't know your piping, but it or something similar (and newer) might allow you to get your eyes inside the exhaust piping to see if water is getting in somewhere where it should not while you have the pipework off the engine.

That is something I have considered, but I'm not confident I could see a small fracture. The crack in my manifold was visible only after I took a grinder to polish it. I think if testing with a vacuum shows I have a leak, an endoscope would be a good investment to determine its location and extent.

[ForeverDes]

Well, looks like the exhaust pipe is in good shape. I plugged the outlet of the water jacket where it mixes with the gas side, pulled 10 psi of vacuum, and it held for 5 minutes.

My next step is to check how much back pressure I have again. I'm waiting on a new piece of wet exhaust hose to connect back to the thru hull on the transom before I do it.

[fourlyons]

OP, reading back over your posts it sounds like you've had the boat for a while and so know for a fact that this is a new problem. Was something changed about the time the problem showed up? You said you cleaned the carb, did you leave one of the jets out? Is the engine getting up to operating temperature, maybe the t-stat is stuck open?

[ForeverDes]

Originally Posted by fourlyons

OP, reading back over your posts it sounds like you've had the boat for a while and so know for a fact that this is a new problem. Was something changed about the time the problem showed up? You said you cleaned the carb, did you leave one of the jets out? Is the engine getting up to operating temperature, maybe the t-stat is stuck open?

When the problem first became obvious, I thought it was a dirty carb/clogged jet. It ran rough/surged, and died suddenly. I totally cleaned the carb, but I doubt that was the issue as it wasn't dirty, no jets were clogged, etc.
The I adjusted it, as well as I could, as per Don Moyer's video (Mine is an older model, and the video was for the newer model) I've made minor adjustments a few times since, but if there's any improvement it's not enough to notice.
I also adjusted the timing by tying to the dock and revving to 1800 rpm in forward, and adjusting for the smoothest, fastest rpm. There was a very minor improvement at best.
I checked compression and had 85psi +/-2 on all cylinders.
I don't have excessive smoke from the exhaust, white or blue, although at one point I had the mixture very rich and had a bluish tint to the exhaust, before I leaned the mixture more.
The only change I've made was replacing the manifold.
I've watched and read about everything I can on the afourians site about this, and low compression, rich fuel mixture, incorrect timing, or exhaust back pressure seem to be the only known causes of fouling plugs.
A few things to add. When I first noticed this, I had badly leaking fuel filter, the water separator, and replaced it. I spent some time when I did to make sure I had no other leaks, or possible air infiltration, into the fuel lines. I also changed from rj8c to rj12c plugs, when I added the electronic ignition 2 years ago. I even tried the hotter autolite (537?) recommended on the afourians site, but switched back to rj12c when I added fwc, since the engine operates at 180 degrees now. I've got a set of rj8c's coming as well. I can easily get 1/2" of spark from the coil to the head (another thing Don Moyer suggests checking with this problem)
I guess I could have a leaking gasket on the manifold. I'll look into that as well.