Sooty Plugs Create Problems

[MikeB.330]

Dave,

Is it possible to feel the difference between the delaminated section of hose from the undamaged section of hose. It would be great if the delaminated secion felt much softer. When I had my MMI A4 installed last summer the mechanic said the old hose behind the Vetus muffler was fine. Now I'm wondering how he could tell. I'm assuming that yours looked fine from the outside.


Good work troubleshooting!


Mike

[daveinrenton]

Mike:

That water/exhaust hose is four layers thick and quite stiff. It was impossible to tell if one section was softer for sure. It probably was also because the hose was who-knows-how-old which would tend to harden the rubber as well. The other thing is when I pulled it off the muffler outlet pipe, it looked fine. As Don mentioned, it was downstream a foot or so before the collapse was evident. The view down the hose is so dark, it would be difficult to see since it is not a rod-straight shot to the transom. Following Don's advice, I cut a foot or so off and intended to replace the offending section if I actually found it there. When I saw the collapse, and after I did a spiritual high-five with Mr Moyer, I decided I wanted no part of having even an inch of the hose remaining. If you do not know the age of the hose (which I didn't), what's fifty or sixty bucks to make certain you know the history and condition from front to back? I can only imagine the spectacular damage that would have been done if the water flow had overwhemed the skinny flow area that was left in the hose and backed up into the engine. Apparently, it was trying hard to do that and, in fact, it is likely that the water volume at the occlusion was literally blocking the exhaust from escaping ultimately making it dog down at medim RPMs.

Don, I am sure the oil was contaminated with carbon as the pistons worked up and down so I am replacing that. With new plugs in, I'll be able to watch the progress and be assured that nothing relating to the prior condition will threaten my safe passage when the "little engine that can" is needed. I've gotten pretty lucky averting disaster and I am loath to press it much farther. I am going to hold off on the jet replacement until I next do a general carburator servicing. It's a bit of a hassle removing the carb since there is so much stuff hanging off of it. I'll report back in a couple of months (on this issue) and let you and the group know that all is well or otherwise. I'm all full of confidence that the correct problem was fixed. That's usually about the time I get fresh surprises!

Dave

[lhbradley]

Effects of back pressure

I had an taste of what back pressure could do a couple of years ago.
The engine ran like a tank. It started fine, but the engine RPM would go up and down by a couple of hundred RPM over a few seconds. It would stall. I rebuilt the card. I replaced the main jet with an adjustable one. I sacrificed chickens to the gods. Nothing helped. At the same time, I noticed that the exhaust water was not coming out in the volume I expected, but the engine was no overheating. And the water volume was pulsating just like the engine RPM. I "assumed" I had a problem in the water system, but I could find nothing wrong.

About two weeks into this problem, there was a loud BANG from down below, and my wife noticed water and exhaust all over the place. Shut down engine, looked around, and found that the Vetus water lift has split on a seam. Got back into a slip, look things apart, and found that the real problem was that a loop I had put in the exhaust hose at the transom to stop water coming back in had a bad kink in it, and had finally collapsed. This blocked the exhaust and the pressure finally blew the water lift. But before that, the increased back pressure had been the cause of all my problems. Once I replaced the water lift and the hose, the engine ran just fine.

[daveinrenton]

Great story, Larry! There is no doubt that all of these revelations will have our fellows checking the exhaust runs first when odd-ball things start happening where the smog and water exit the boat. It'll save a lot of chickens, too!

Dave

[Jeff in TO]

Awesome thread, Gentlemen. I will certainly take a look at mine!!! Thx for the shoutout, Don.

Jeff

[Bill McNamara]

Exhaust System Check

Hello All;
Thanks Don, et al for the "heads-up" Re: backpressure. While I have replaced the black iron components of my A-4 ('78 C&C 34) system a few years ago, I've not checked downstream of water lift muffler since purchasing the boat 20yrs. ago! Its on my "to-do" checklist for this spring, for sure.
I haven't had any of the symptoms/problems described herein, and want to keep it that way.

Bill McNamara
"Miss Conduct"
Picton, On. Can.

[brad@elevated.org]

next thought is the muffler

Dave- You have the same vertical muffler I have, have you had to relapce it too- that is apparently an uncommon design. Do you have a local Puget Sound supplier.

Brad

[daveinrenton]

Apologies, Brad. I did not know folks were still responding to this thread after the concluding segments. My standpipe muffler is still fine (1979 Ericson 29). I looked over all of the joints for anything suspicious looking and found nothing odd or overly rotten including the little rubber vibration isolators. When I had the boat surveyed several years ago, the surveyor suggested replacing the standpipe with a "water-lift" muffler. So, if the old bugger ever gives it up, I'll probably go that way. It's a more modern and supposedly more safe design. But since I have had no problems with it and it runs as quiet as can be (one of my friends calls it the "stealth engine"), I'll hang with it.

Dave

[David Conroy]

Thanks

This thread solved my problem. For four years, the A4 on my 1977 Pearson 28 ran OK and then developed a stalling problem. I had sooty plugs. I found this thread and looked at the wet exhaust hose. It was old, but seemed intact by sight and touch. I removed it. I didn't want to cut into it, so I took a hose with a pressure nozzle on the dock and ran water through the hose in each direction. From back to front, the discharge stream was just like it comes out of a faucet. From front to back, the discharge stream was slightly irregular. Bridge Marine on City Island cut me an 8' 2 & 1/2" piece of 1 & 1/2 " interior diameter wet exhaust hose for $65. I installed the new hose. The volume of water discharge immediately increased and the engine runs a bit cooler. Over an hour's use, the stalling problem lessened and then disappeared.

This was a simple and inexpensive part replacement. Like DaveinRenton said, I can't imagine why anyone would want to run with an old hose.

[Dave Neptune]

Cool

David nice job and welcome to the forum! This is a really old post and a handy one at that.

Dave Neptune

[macgyro]

Similar symptoms, no exhaust blockage

Hi guys,

I know this thread has been inactive for a while, but the symptoms described were exactly what I was experiencing at the end of last season. My RPM wouldn't go above 1800 RPM and it sounded like the engine was flooding/bogging down. It started funny, sometimes with no choke, sometimes it wouldn't run without choke, but never ran quite right.

I tried different twists of the mixture control jet screw thing on the aft end of the carb, different choke settings, etc. Then I pulled the plugs, and the forward 3 were black and sooty with the aft-most slightly white.

I found this thread and, the next day, removed my exhaust hoses to try to find the blockage. All of the hoses were fine, so I blew into the muffler and launched a fountain of glycol all over the cockpit of the boat. Then I removed the dry exhaust section from the manifold. No blockages anywhere, including the thru-hull on the transom (Ericson 32).

Could the exhaust blockage be in the manifold?

Part 2:
Early last season, the engine started to overheat (200 degrees) and I installed the cooling bypass line with the shutoff valve and used it with the bypass valve mostly closed. Then, the engine ran too cool and would rarely get up to temperature but was still running fine (up to about 2200 RPM on my tach. I don't think the tach is set right) I was nervous about running for a long time with the valve completely open in case I forgot to monitor the temperature and it climbed again. I got a new thermostat this winter, so I'm hoping to keep the valve open and it will work.

That was a long story, but since I ran the engine for most of the season too cool, I'm wondering if that could have fouled the plugs enough alone to cause my symptoms without excessive exhaust backpressure?

If anyone's still out there, do you have any ideas?

Thanks!

Dean

[Dave Neptune]

Dean, I suggest a new thread. It sounds like one of two things or possibly both. First the idle screw will only affect the idle circuit and it sounds like the carb is running way rich to cause sooty plugs. A good look at the carb is in order and a thorough cleaning.
Second is timing. Timing can be way off if the points (if still equipped with them) and the cam are worn down a likely senarior due to the age of the motor. Check the "dwell" not the gap in these old engines!!!! Be sure you have a good "blue" spark and set the timing or just try a bit of "advance" to see if it helps.
The right fuel mix (carb)~good blue spark~and the spark being delivered at the right time (timing) equals a good running engine!!
Other notes connected to the above. Make sure the centrifugal advance is working inside the distributor~ a fresh cap and rotor~fresh plugs~plug wires in good shape. Also do a visual to be sure the choke is fully opening and closing.
I don't see how the manifold itself could create a blockage inside.

Dave Neptune

[wakemutant]

How does one inspect the various pipes in the exhaust line to ensure no obstructions? I have a good old stand pipe muffler with the coolling water ejection BRAIDED LINE (8 PLY) SEA STORM - MZBL8YW-XXX at the top of the standing system as is common. Should I just start yanking things apart? What should I be looking for?

[ndutton]

How does one inspect the various pipes in the exhaust line to ensure no obstructions?

Exhaust back pressure gauge.