Fouled plugs! (again)

[theredboat]

After some recent major changes to my engine, I've started fouling plugs after about 1-2 hours of use. Seems to happen under load and idle. The symptoms are engine starts misfiring, as if she is starved for fuel, and then she ultimately stall.

This was not happening before the changes. I've been going back and reading all the posts about fouled plugs trying to eliminate all the possibilities, but I thought I'd go ahead and try to get some feedback from you guys... Here's what I've done recently, not sure which items may have caused the plug fouling:

1. Removed and replaced head and head gaskets w/ new moyer ones
2. Fully took apart carb and cleaned it
3. New coil (I bought this from napa and didn't check the ohm rating with a meter yet... is this a potential culprit?)
4. New plugs (same J8C that was originally in there)

After these changes I started getting fouled plugs. Since then I've done the following to try and fix the issue:

1. Took apart and cleaned carb again
2. Set timing by rotating distributor at cruising speed
3. Tried hotter RJ12C plugs
4. Reset idle mixture screw and set idle RPM (I could not get it to idle right at 800 though... more like 950rpm if my gauge is right)
5. Adjusted choke linkage to make sure it was set properly

Throwing in a new set of plugs instantly fixes the issue, so I have to believe that that's the only problem.

[ndutton]

Others may already have some ideas but as for me, I have more questions:

1. Head and gasket replacement - would like to see compression test values.
2. Cleaned carb - you've done it twice so I'll leave it for now.
3. New coil - do you have points or electronic ignition? Makes a difference in the coil.
4. New plugs - don't think they're the problem but rather that the problem is damaging them.

[theredboat]

I don't have a gauge for compression test at the moment, but will acquire one and report back.

It's points, no electronic ignition.

[hanleyclifford]

Neil is right about asking questions and that is how we get to the bottom of these issues. You mentioned that you have points, not electronic ignition. Do you know what your dwell angle is? Are the points clean? Do you have a spare condenser just in case. The only way to know about them is to change to another. The fact that throwing in a new set of plugs fixes the problem (apparently temporarily) suggests a weak spark that does not keep the plugs clean very long. If you don't have a dwell meter I would suggest getting one for your on board tool kit together with a timing light. The specification for initial timing is TDC.

[msauntry]

With respect to HC, I'd skip the dwell meter and just go for the electronic iginition upgrade. It takes about 30 minutes to install.

Consider how much time and money you've spent so far chasing this problem.

[Dave Neptune]

Adjustment??

theredboat, do you know how to properly "adjust" the idle? And do you have the float set properly. The idle adjustment can cause fouling but they can still run clear at cruising speeds. Try shutting her down abrubtly after cruising for a 1/2 hour or so and look at a plug or two. This will let you know if it is an idle or hi speed jetting problem. I have found the carbs pretty forgiving but sensitive to float adjustment and fuel preassure.
Are the plugs "sooty" or oily???

Dave Neptune

[High Hopes]

Assuming the plugs were OK before, I suspect something got bungled with the cleaning. There are so many little parts and even small specks of dirt are problem. Buy a new carburetor.

BTW, electronic ignition is a must have. Points went out in the sixties.

Good luck. (please remit 2 cents)

[hanleyclifford]

In the fiftys we still got two cents back out of the machine when we bought a pack of cigarettes. Ok, let's not be dwelling in the past.

[JOHN COOKSON]

R\E Fouled Plugs

Pictures or a description of what is fouling the plugs would be helpful.

Check the spark by closing the points (key on) and flicking them open and letting them snap close while holding the lead from the center of the distributor near the engine. If you can throw a 3/8" to 1/2" arc you are getting a good healthy spark and the coil is probably ok.

You can clean fouled plugs with a spray can of either based starting fluid. Take the plug out and spray the electrode. Cleaning plugs will save you $ till you resolve the fouled plug problem.

To get nitpickey for just a second - did you double check the carburetor to be sure the choke is all the way open?

TRUE GRIT

[rigspelt]

Not getting enough sleep lately, but what nobody has brought up exhaust back pressure as a possibilty. I know that would be a coincidence, given the recent changes, but could that be an issue?

[dcstait]

check the pitch on the prop

My fouled plug problem was solved by getting a 3 blade prop that
decreased the load and increased the rpm.

[Mo]

Good show.

Well, there's a bit of info to stick in the back of my tiny little mind

[Bingy]

I've been working on two boats with A4s.
Installed NGK plugs in both ,set gap at 35 th. and both boats had fouled plugs shortly there after.

Replaced plugs with Champions
and both are running fine.
Should I have made other adjustments when using the hotter plugs that failed.

[Sony2000]

#4 in after these changes: suggests you should do it again, but try this....
Idle RPM screw should be backed off, so as to NOT touch the carb.
Run the engine and back off the idle mixture screw until just before the engine starts missing.
Your excess carbon is no longer.
Now, maybe, set idle RPM screw.

[romantic comedy]

You want to get it running on the points system before considering electronic ignition. You dont want to complicate the problem.

These engine will run fine with points.