Engine dies after running for several minutes

[bbook83]

My 1974 140/3.0 liter starts and runs well for 10 to 12 minutes, then shuts down, usually with one short surge as it is dies. It first did it last summer, so I replaced the fuel pump, confirmed clear fuel lines, cleaned the tank take up tube, elbow, and ball check valve, treated the fuel with Heet, pumped a quart off with the starter to a jar and saw no water. Over the winter, I had the carburetor rebuilt, and the first time in the water this year, drove about 10 minutes from the launch to my dock and thought all was well, but the engine died as it did last year shortly after. It can be restarted after a short time, but then dies after a much shorter time while warm. Today, I adjusted the points, but no change. The distributor has some side to side play, but I don’t know if that is an issue. At this point, it appears that the problem is heat related. Should I be looking at the coil or the distributor? I think I have done all I can on the fuel side. Any ideas out there?

 

[alldodge]

Has the condenser been changed?
Does the coil get hot?
When its running, measure the voltage on + side of coil to see if its around 9V
Also when it dies, does the voltage change?

 

[bbook83]

Has the condenser been changed?
Does the coil get hot?
When its running, measure the voltage on + side of coil to see if its around 9V
Also when it dies, does the voltage change?

The condenser has not been recently replaced. Everyone always tell me they seldom need replacement. The coil is not hot to the touch. I will measure coil voltage when running and after it dies when I get back to the boat. Thanks for the ideas Alldodge. Am I correct that the ballast resistor is in the wire going into the coil positive post, and that there is no resistor in the coil? I looped excess coil wires together with a zip tie, including the one marked “resistor”. Could that have created a problem?

 

[dubs283]

The condenser has not been recently replaced. Everyone always tell me they seldom need replacement. The coil is not hot to the touch. I will measure coil voltage when running and after it dies when I get back to the boat......Am I correct that the ballast resistor is in the wire going into the coil positive post, and that there is no resistor in the coil?

Probably time for a full tune up, points, condenser, cap/rotor, plugs, wires, fuel filters, etc..check and set dwell/timing/idle. Yes, if your setup is oem most likely the engine wire harness has the resistor wire in it. There is still an oem replacement for said wire if testing shows it to have failed...

 

[alldodge]

Condensers do last, but I always change because its a cheap item.
Correct there is no resistor coil. Measuring the voltage will tell us if its loosing power and if running correctly. Might be something simple as a bad connection or my key switch

 

[bbook83]

Condensers do last, but I always change because its a cheap item.
Correct there is no resistor coil. Measuring the voltage will tell us if its loosing power and if running correctly. Might be something simple as a bad connection or my key switch

So, after chasing potential fuel issues for the problem, I came back to ignition. Voltage at the battery is 12.4 volts, at the end of the white wire coming from the harness plug, it is 11.6 volts, and at the + side of the coil at the end of the long multi looped resistor wire connected to the white wire is 4.9 volts, all with the key in the run position. Other posts suggest that the resistor wire should only bring it down to 9 volts or so.
There was a bad connection where the two wires going to the + side of the coil came into one connector, so I replaced that with two separate connectors. Runs great on the hose, but I have not run It under load for any period of time.

Hopefully the bad connection was the problem, but should I be concerned about the 4.9 volts at the coil? Could I just shorten that wire?

 

[alldodge]

Seeing the 4.9V not so much with motor not running. Does it show the same running?

 

[bbook83]

I will check tomorrow on running voltage and report back.

 

[bbook83]

Sorry for the delay. I checked the voltage with the engine running and got 13.5 volts at the battery, 13.9 at the connection to the beginning of the resistor wire, and 11.3 at the positive side of the coil. Do these sound ok?

 

[alldodge]

Should have around 14.5V at the Bat, might be an Alternator problem

11.3V at the coil is a bit high

Does the coil get hot when running?

 

[bbook83]

The coil has not gotten hot, that I can detect. If voltage is high at the coil, is the resistor wire potentially not doing the job correctly?

 

[bbook83]

Would I be better off eliminating the resistor wire, in favor of an internally resisted coil?

 

[alldodge]

I would leave it as-is, the boat has not been tested on the water. You did a tune up so it might be just fine

 

[bbook83]

I will test on the water and report back.

 

[bbook83]

Checked the ohms on the resistor wire at 2.1. My understanding is it should be 1.8 to 2.0. Put the boat in the water and it died about 10 minutes from the launch. Coil was not hot to the touch. Voltage at the plus side of the coil was 11.4. Thinking of replacing the resistor wire, but really do not have many answers. Engine was flooded when first started, so fuel system is not perfect. Truth is, I have a full electronic ignition I bought last year, including new distributor and coil. I just wanted to solve the problem first, without adding new variables by way of installation errors. Opinions are welcome.
,

 

[alldodge]

With points ignition 11.4V should not have been an issue

Does appear something is killing the spark, we just haven't found it yet. Might be a loose connection. The way it's acting I wouldn't be surprised if electronic ignition was added it would also do it. Might not only because lower current draw, but would probably show up some time later

 

[flashback]

Clean up or replace points, replace resistance wire...11.4 will bugger the points.

 

[flashback]

It's been a decade or two since I played with these so , in the past you needed to find around 9 v at the coil to protect them from arching... sorry I meant the distributor..

 

[flashback]

They had a flat looking wire that reduced the voltage..

 

[bbook83]

I ordered Mercruiser resistance cable assembly/kit 84-94227A. Looks like it is for later models with the electric choke, but I can make it work as long as the resistor wire is there. I will examine the points and condenser tomorrow to se if the 11..4 volts did any damage.