Engine Dies after Running

[Captain Soames]

The following is the present maintenance of our Atomic 4 located in our
C & C 33 MK 1.

New Points installed 2003
New Plugs installed 2005
New High Tension Wires 2001
New Distributor Cap 2003
Engine Oil Changes Twice Annually
Fuel Filter Changed 2005
New Electric Fuel Pump 2002

Problem: Engine has suddenly died after 4 hours of running upon entering
anchorge. This was first time in 2005
Engine has suddenly died after 13 hours of running upon entering
home harbour. This was second time in 2005
Engine has suddenly died after 30 min. of running upon entering
home harbour.
*** All three above occured after a period of running at 5 knots
then reducing throttle to 1 - 2 knots or back to idle.

Solutions: Can this problem involve worn points?
Can this problem carborator issues?

[LastLeg]

Same Proble

I have an A-4 1970 Vintage on an Irwin, Brand New Alternator (from MM) and points, plugs and wires.

The engine runs for about 1 hour dies, it will not restart and appears to have no spark, once it cools it starts right up and will run another hour.

I heard on this board that an internal resistor coil is needed instead of and external resister coil. I am not sure what this means, I did change the high voltage coil to one found off the shelf of a local autoparts store.

[Don Moyer]

Unless you have a large porcelain external ballast resistor in the circuit between the ignition switch and the positive terminal of the coil (which would be quite unusual), you should be using a coil with internal resistance. If you have a digital volt/ohm meter, you can measure the resistance across the primary terminals of the coil. The resistance should be 3 to 4 ohms for an externally resisted coil, with the wires removed from the coil.

The next time your engine stops, run through as many of the following steps as you can before the engine will restart:

1) Use a volt/ohm meter to check for the presence of 12 volts between the positive terminal of the coil and ground (with the ignition switch on). It's best to continue checking voltage at the positive terminal of the coil while cranking the starter. The voltage may fluctuate between 10 and 12 volts as the points open and close. If you do not have power at the positive terminal of the coil, troubleshoot the primary ignition circuit within your boat's electrical system. If you do have normal voltage at the positive terminal of the coil, go to step (2) to check the engine mounted part of the primary ignition system.

2) Remove the distributor cap and rotate the engine until the points are closed. Remove the secondary lead from the center of the distributor cap, and hold it approximately 1/4" from the cylinder head. Take a pencil or other pointed (non-electrical) tool, and open and close the points. Each time you open the points you should see a small amount of 12 volt arcing at the points themselves, and a strong secondary discharge between the end of the coil lead and the head. If there is no secondary discharge in this test, the problem is most likely a defective coil.

NOTE: With electronic ignition installed, perform steps (5) and (6). Each time you rotate the distributor across the point where the test light goes off in step (6); there should be a secondary discharge from the coil lead to the head.

3) If you observed a good secondary spark in the preceding step, your problem is likely in the secondary part of the system, downstream of the coil. It's rather difficult to separate problems within this part of the secondary ignition system. For this reason, it's usually best to simply start replacing these secondary components one at a time starting with the plugs, distributor cap, the wiring harness, and finally the rotor.

Don

[Don Moyer]

Captain Soames,

The only thing I can think of that might explain your shut downs (presumably at or near idle) is that the idle mixture might be on the lean side and doesn't pick up the load as you come back past 1100 RPM or so. If turning the idle mixture screw in a half turn or so doesn't cure the problem, I'd check the two idle ports along the side of the top of the carburetor throat to see if one of them is clogged (especially the lower one).

At approximately 1100 RPM, the main discharge nozzle pretty much drops out and the idle system is supplying most of the fuel to the engine, and if the lower of the two idle ports is clogged, the mixture will become very lean during the transition to idle. If the engine can get to idle, and the upper port is open, it will able to carry the load, but only at around 800 RPM.

This situation is sort of like a flat spot during acceleration, only in reverse. The lower of the two idle ports is referred to by some (including the writer) as the "off idle" port, because this port has to kick in as you move the throttle forward to get you "off of idle" and on to the main discharge nozzle. If the lower port is clogged, you'll feel a flat spot until you get to the main discharge nozzle - if you can even get to the main discharge nozzle.

As you decelerate, you're depending on the lower idle port once again to kick in to carry you smoothly as you transition between the main discharge nozzle and the upper idle port.

Don