Sooty Plugs

[roadnsky]

So what would be the advantages of that? Better mileage?

Yes
AND, possibly in Joe's case, less sooty plugs and a more normal setting (1.5) on the idle mixture valve

[ndutton]

I am not advocating any change to the float setting beyond the instruction found in the MMI manual. My entire input in this thread has been to examine what might be WRONG to cause sooty plugs and an idle mixture screw setting of 2½ turns off the seat (typically 1¼~1½ turns).

While we are discussing the float setting in detail, don't forget the possibility of a leaky float affecting it's buoyancy in the carb bowl.

[roadnsky]

Hey Joe-
Can you take a voltage reading at the coil (engine running) the next time you're at the boat please?
I'd like to verify that you don't have a low voltage issue caused by your loose alternator belt.

[roadnsky]

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?

Thoughts?

Bumping my earlier questions to the smart guys again...

[SubtoSail]

Some updates from my afternoon at the boat today:

Unfortunately, I didn't have time to get into the carb, so that will have to wait until next time, hopefully Thursday.

I replaced the sending line to the tachometer, and it seems to be tracking well, plus or minus about 100 RPM is my guess. I'm currently idling at about 900RPM, which might be a little fast. Using the throttle adjustment screw, not the mixture screw, I dialed it down to about 700-800, it continued to run, neutral reverse and forward. 900 sounds a lot stronger and more confident to me, so I decided to leave it there. Lower just gave me that uneasy feeling.

I did notice what I would describe as surging when at idle. It may be completely in my head, or it may be real. It sounds as if the engine is revving ever so slightly, less than 100RPM, up and down, not really in a predictable pattern. My theory on what could be causing this, other than my own paranoia, is something in the carb. Could be an obstruction somewhere, or it could be completely normal. If it's normal, my guess is that it is the engines response to the float level in the carb changing. Level drops as the motor runs, then revs slightly as the float opens and the fuel pump pumps more fuel in. Have I identified a problem here, or just learned something that is common knowledge?

The exhaust leak continues. I was able to sand the old gasket chunks off the flange, but the new gasket has deformed, likely due to the exhaust gas pushing around it, and doesn't make a good seat. Hopefully a new gasket will solve this problem.

Coil is new from MMI, and measures 4.2 ohms with nothing connected to it. Voltage at the positive post with the engine running was 14.2V, no change with change in RPM, which sounds correct to me. That yields 3.38 amps to the EI, which I believe I have read on other threads is normal, but any additional advice on that is definitely appreciated.

As for the loose alternator belt, it looks like the alternator is set as far up on the arm as possible. That means that either the belt is stretched and past its prime, or too big. I did find a presumably unused one on the boat, 25", but the cardboard it was wrapped in looks pretty old, so no harm in getting a new one. Unfortunately, I don't know which alternator I have, as there are no markings on it. I've included some pictures in the hopes someone has some experience with it. It looks pretty hefty, certainly larger than the starter.

Down to the plugs. I took updated pictures of the change I've noticed. The picture is somehow upside down, so they are one to four, right to left. They are RJ12-C, and have been in for 9 hours. I see whitening on the insulator around the center electrode, on one half of the plug. I see it on all four plugs, but more so on the more forward ones. I also notice what looks to me to be some cleaning action on the ground electrodes of 1-3, but that could be wishful thinking. I don't really know what either of these mean, if anything. Could this be an indication that whatever the soot causing condition was has cleared, and the plugs are on their way to cleaning up?

In summary:
1. Idle RPM thoughts
2. Surging
3. Any possible effects on engine performance of the exhaust leak
4. Coil voltage at 14.2V
5. Alternator assistance
6. Plug assessment

As always, thanks for your time and help!
Joe

[roadnsky]

Hey Joe-
Good report!

I think your numbers on the voltage are good.
Others with better knowledge can comment further but that's pretty close to what I have on my boat.
I was worried that belt would cause a low voltage but...

Speaking of the belt and that alternator...
It looks familiar.
I'll do some researching but someone here might know before I find it. (hint, hint)
Also, there is a really cool tensioning device you might want to consider sold here on the MMI site (invented by our Neil too)

I think your report on the idle jives with what I remember and you're really close to having it dialed in.
Once you get the carb done, let's see.
Also, let me know how that TACH holds up. (My offer still stands)

I agree the plugs do look a little better to my eye, but again, let's wait until you've attacked the carb and see what you find.

My prognosis (FWIW) is that you get the carb cleaned up and hopefully there is a small adjustment needed on the float setting that makes the difference in your idle mixture.

Keep at it. You're already a pro at this!

[ndutton]

Delco 10Si Single Wire (self excite) ignition protected

[roadnsky]

Speaking of the belt and that alternator...
It looks familiar.
I'll do some researching but someone here might know before I find it. (hint, hint)

I knew that Neil was listening

[ndutton]

I knew that Neil was listening

Just tryin' to be helpful . . .