Sooty Plugs

[SubtoSail]

Experts,

I'm almost ready to throw in the towel and mount an outboard, but not quite yet. I'll give the life story...to start shes a 1970 late model, mechanical fuel pump, EI, raw water cooled.

I'm having some reliability issues that I've been chasing for awhile now, and I thought it was all related. I've had the boat for about a year and a half, mostly trouble free. She wouldn't start to get us into our new slip on our maiden trip, replaced the spark plugs and she was running. Next trip she died, in response I rebuilt the carb with new jets, and replaced the fuel filter. Trouble free for about a year.

Fast forward, we get put back in the water after a haul out, she took a few more turns to start than normal, but she starts. We start the trip back, find that we're in over our heads and decide to motor, but she won't start. Replace the plugs and she starts, but dies after about a minute. We get a tow.

Discover that in our desparation we flooded the exhaust. At least there is a procedure for this. Drain the exhaust, change the oil 5 times, MMO the cylinders, clean the carb, compression check. Cold: 100, 70, 85, 100, warm: 100, 100, 115, 115. Shes running, let her go in the slip for an hour, throttle, idle, forward, reverse. We motor for two hours to get to our own marina. The last twenty minutes she starts to lose power. Felt like a cylinder shut off, more throttle and it comes back. Happens three times, eventually with full throttle she dies. We get a push into the slip, and she starts up.

At this point I think fuel problem, so I replace the filter, rebuild the mechanical fuel pump with the moyer kit, add the in line polishing filter, clean the carb, and replace the coil for good measure. She runs fine for an outing or two, then while pulling out of the slip she died as soon as I put her in reverse in idle. She would run with gas, just not idle. I found I had the adjusting screw 3.5 out, set it to 2.5 and now she's fine.

All four plugs are still sooty, and I believe this is all somehow related. I just took the exhaust apart, thinking blockage. Unfortunately, it all looks clear, not the best design in terms of height, but there does not seem to be a blockage.

Call me paranoid, but even though she starts up and runs right now, I don't trust her. The plugs are still fouling, which makes me say back out the adjustment screw, currently at 2.5 out. Any more out and she dies. I could remove the fuel and tank for cleaning, but she seems to be getting consistent fuel without water. All i have done on the ignition side is replace the distributor cap and coil. Could this be a timing issue?

The boat is just about 50 years old, and only used for day sailing. An outboard is looking more and more attractive.

Thanks for the help you have all provided so far!

[Dave Neptune]

The only advantage to an OB is you can take it home to work on. Allso be aware that is no simpler to work on or diagnose!!

The first thing I would do is take a look under the distributor cap to check for a clean cap & rotor and be sure the centrifugal advance is working by giving it a twist and "it's" springing back smoothly.

If the plugs are sooty it means she is running rich. Take a VISUAL look at the choke to be sure it is backing off completely.

Now if you are "idling" and the air screw was out 3 1/2 turns you should be very lean and at 2/1/2 still lean. Most of these idle at around 1 1/2 turns out.

Sounds as if there may be something inside the carb plugging an air jet. But first do the above.

Have you tampered with the timing? Do you have a crisp blue spark?

Dave Neptune

[JOHN COOKSON]

A dirty back flame arrestor will also cause rich running.

TRUE GRIT

[SubtoSail]

I have done nothing with the timing. Certainly could be contributing, as I believe I bought this problem with the boat.

Spark seems fine. The choke plate goes back horizontal when released. I actually don't have a cable to the choke, so I push and hold the lever back manually when cold starting. I almost immediately release the choke upon starting and then work the throttle down. She usually will die in idle until she's warmed up, which I believe is normal.

I spray the flame arrestor with carb cleaner when I clean the carb. Some amount of light can be seen through it when held up to a light. I'm not sure how clean that makes it, I've only seen one of them. I suppose I could test it by running the motor with the screen off and see if the mixture screw needs moving.

It may be worth noting that the plastic tube from the block down to the flame arrestor doesnt have that turn down, it just points straight out. If this is effecting the mixture at all, my guess is it would be a very minor effect.

[SubtoSail]

I should also mention there is a hiss that comes from the carb, paricularly at idle. It is a pretty distinctive sucking sound. When I put my hand over the flame arrestor the sound dampens, so definitely coming from the carb. Removing the flame arrestor does not change it. I haven't been able to find out what, if anything, it could indicate.

[capnward]

It should idle before it's warmed up. If it doesn't, it's too lean. That could be the idle screw out too far, or the carb gaskets leaking, which would also explain the hissing sound. Does the choke close all the way? If not, that would also explain a lean mixture leading to hard starting.
Since you put in new jets a year ago, some crud in the fuel may have gotten past the filters and obstructed the jets. The idle jet is the narrowest, and when that is even partially clogged she won't idle. Run a thin wire from a wire brush around in the jet to clear it. If you want to make sure there is nothing in it, you will have to carefully remove it with the right size screwdriver, and hold it up to the light.
From what I understand, turning the distributor clockwise retards the timing, which richens the mixture, too much can foul the plugs. When you get it running, turn the distributor at cruising speed under load and see what setting gets you the most rpm.
I have heard that having the idle mixture screw 1 turn out from the seat is often enough. Turning it out leans the mixture. If you have an adjustable main jet, turning it out richens the mixture.
IMO, it's better to keep learning about the simple engine you have, than to start over with a new outboard. All engines are dependable until they aren't.

[SubtoSail]

If the mixture is actually lean, based on the idle screw out 2.5 and some stumbling at idle, what would be causing the black/char/soot on the plugs? Could that be timing?

Last time I adjusted the screw I started at 1 out per the book, and it died when taken back to idle. 1.5 might have kept her going, but about 2.5 sounds the best. With the screw out more than expected, that would indicate not enough air is getting in, and the screw out is compensating, resulting in a good mixture. But the plugs still foul, indicating rich.

There certainly could be multiple issues happening, which of course makes troubleshooting and assessing indications difficult, so thanks for all your help and thoughts.

[JOHN COOKSON]

My $0.02; I'll Go With Dave N.

The first thing I would do is take a look under the distributor cap to check for a clean cap & rotor and be sure the centrifugal advance is working by giving it a twist and "it's" springing back smoothly.
Dave Neptune

Post # 2 quote above.
Before you even think that the problem might be with the fuel system be sure the ignition system is correct - timing, dwell, and advance.
Some try to correct ignition system problems by changing the fuel system to compensate ie by changing the idle speed and or mixture.
START BY ENSURING THAT THE IGNITION SYSTEM IS CORRECT.
After the ignition system is correct then try adjusting the idle speed\mixture.
If you can't achieve a satisfactory idle then rebuild the carburetor.

TRUE GRIT

[roadnsky]

StS-
I just noticed you're in Oahu...?
Where'bouts?

I'm over in Punalu'u vacationing until next Thursday.
Maybe I can come take a look if you want?

[SubtoSail]

Sounds like I'll go through the ignition side first.

Jerry, the boat is in Kaneohe, moored across the bay from you. Although I'd hate to ruin your vacation with tinkering, I wouldn't say no to a more experienced set of eyes and ears

[roadnsky]

Ok, you're on the "right" side of the island then.
Let me discuss it with the "Admiral" and see how she feels about me going out and doing "boat stuff"...

[roadnsky]

Sub-
Check your PM...

[roadnsky]

Warning, long post but there’s a lot to cover

I hooked up with Joe yesterday to take a look at his A4 setup...

Without giving away too much personal info on Joe;
he’s a great young guy who is in active duty serving our country
(his screen name gives you a hint)
with a clean 27’ Newport with pretty decent engine access.

First thing we did was open up the distro cap and check the springs/weights.
They were pristine and nicely lubed.
The cap is brand new and looked fine. (See pic)
The plug wires are in the correct order and in good condition.
Checked the choke and it is opening and closing fine.
Flame Arrestor is good but for initial testing we left it off. (Later, tested with it on)

So we fired her up and she ran really well. Started right up within 2-3 seconds.
Did a couple of throttle revs and she did well. Slight hesitation but good.

There is a small but definite exhaust leak at the flange/manifold joint.
Water flow was very good at the exhaust.

Shut it down and pulled the plugs. They’re definitely sooty. (See pics)
Not wet, just carbon burned. (More on this later)
We gaped them to .040 and re-installed them.

The Idle Mixture screw was indeed at 2.5+ turns out.
Re-set it to 1.5 for a baseline while checking the timing.
Fired her back up...
We didn’t have a timing light, so we ran her up to speed (under load) and did a “power time” rotating the dizzy.
We moved counter-clock (advanced) to err on the lean side.
While still running, we tried turning the idle mixture IN and she got rough.
Turned it OUT and she immediately ran noticeably smoother.
Ended up about 2 ¼ turns OUT.
Finally we adjusted the idle screw to a really smooth idle at around 700-800 RPM.
(Tach isn’t accurate so RPM is “by ear”)

So, after the fine tuning, she definitely sounded and ran a bit smoother.
Did some more throttle revs and she did real well. No hesitation or stumble.
NOTE here...
Smoother - meaning running really well.
Many on this site would wish for their engine running this well.

A few questions I have...
Would that Exhaust Leak be causing the sooty plugs?
Could that loose belt cause the ALT to put out low voltage resulting in rich running? Sooty plugs?
(I didn’t think to check voltage at the coil. My bad)
I also forgot to check if Joe is using the CORRECT spark plugs.
They were Champion and the pics show a 2C, so I think they’re right. (RJ-12C)

Joe is happy with the smooth running engine and is committed to the value of his A4 (vs using an OB)
He has an excellent grasp of the A4 and it’s various systems and functions.
He is very capable and willing to do the servicing tasks as required going forward.

He is just concerned, as anyone should be...
Why does the idle mixture want to be set so LEAN?
Why the sooty plugs?

Summary:
• New Sierra 10m Filter/Separator
• New Polish Filter
• Rebuilt Mechanical Fuel Pump
• Carb was rebuilt recently and “looks” clean
• New MMI 4Ω Coil
• New Distributor Cap
• Small exhaust leak at the manifold/flange (Good water batching tho)
• Very loose Alternator Belt (1.5 - 2” deflection)
• ALL plugs are dry, black sooty after approximately 15+ hours
• Idle Mixture setting wants to be on the Lean side. 2 ¼ turns out
• Engine starts right up and runs smooth

So, I have reached the limits to my “mechanical” knowledge here.
It’s time for the smarter guys to step up.
Thoughts?

[Administrator]

Without giving away too much personal info on Joe;
he’s a great young guy who is on active duty serving our country

S2S:

Thank you for your service.

My son is stationed at Tripler.

Bill

[ndutton]

Carburetor float level?
Leaking floats?
Exhaust back pressure?