Distributor wire trips breaker

[maynerd1021]

I have a 1973 Mercruiser 165, inline 6, sn 3557481. I took it out for a couple of hours. It sputtered when shutting down after I turned the key off. It cranked and tried to start, and then it tripped the 40 amp breaker.

The breaker reset after I unhooked the battery. I volt meter test a bunch after reading on this forum, but now the breaker trips as soon as I hook the diatributor wire up from the coil. I cannot find the ground/short issue. Any suggestions?

 

[alldodge]

now the breaker trips as soon as I hook the distributor wire up from the coi

I would say the breaker is bad

 

[Fishermark]

I know a somewhat common issue can be the tach grounding out and causing a problem. Try disconnecting the wire to the tach and see if that clears it up.

 

[maynerd1021]

Thanks, I will try the tach. I am not sure on the breaker though, because I hooked a 40 amp fuse in its place, and it blew immediately

 

[alldodge]

hooked a 40 amp fuse in its place, and it blew immediately

Always good to have as much info as possible. Its not the breaker in this case

Your motor has an amp meter and power goes to the amp meter before going anywhere else. Then goes to key, gauges and back out to motor. Look for wires that are caffed. Here is the wiring diagrams

 

[maynerd1021]

Alldodge, thank you for your help. Sorry I did not include all the info...here is what I've got: I did not find any issues in the instrument panel, except there is a red wire loop hooked up to the white wires coming out of the harness cluster and the ignition switch. The white wires are long enough to connect, so I connected them.

I hooked everything back up, and the breaker did not trip. I attached the muffs and crancked the engine. No start, no tripped breaker. I began working through the no start scenarios in my Seloc manual. No spark from the coil wire 1/4" from ground. Pulled the distributor cap and closed the points. Sizzling sound and smoke came from under the distributor, and the breaker tripped before I could unhook the battery.

Any ideas? Is the coil bad, or the distributor? Should either of them being bad trip the breaker?

 

[alldodge]

Pulled the distributor cap and closed the points. Sizzling sound and smoke came from under the distributor, and the breaker tripped before I could unhook the battery.

Shorted condensor
Check which wires are connected to each side of the coil

 

[maynerd1021]

First, thank you for all your help. I am pretty handy with cars, but I am new to boats.

Coil wires: a white and a tan wire attached on the positive side, 2 Brown attached on negative side, a much smaller wire on the negative side going to the post inside the distributor. The condenser wire was smashed under the distributor cap, so I got a new condenser from the local boat shop and replaced it...still tripping the breaker when the points close.

Should the coil to distributor wire be the same gauge as the other coil wires? Also, is there a ground strap somewhere that I should check? Last, the black wire leading from the alternator has a connector in the middle of it that looks like it should bolt to the block. The connector is melted and no longer attached. Is this an issue?

 

[alldodge]

Only thing left is the coil is shorted

Test as follows

Step 4: Test the ignition coil’s primary ignition circuit. Ignition coils have two circuits that need to be checked: the primary and secondary ignition circuit.


Connect the positive and negative leads of your multimeter to the positive and negative terminals of your ignition coil. On some coils, the terminals will be explicitly marked positive and negative; others will simply have the two pins or terminals that are located at the connector.


Most ignition coils should have a primary resistance falling somewhere between 0.4 and 2 ohms; however, refer to your manufacturer's specifications for the correct reading. If a reading of zero is displayed, that signifies that the ignition coil has shorted internally in the primary windings and needs to be replaced. A reading over the specification signals that the ignition coil is open, which would also indicate a need to replace the coil.

Step 5: Test the secondary circuit of the ignition coil. Connect your multimeter to the positive terminal or pin of your coil, and to the high output terminal that goes to the spark plug.


Most ignition coils should have a secondary resistance falling somewhere between 6,000 to 10,000 ohms;however, refer to manufacturer specifications for the correct range. If a reading of zero is displayed, that signifies that the coil has short circuited and needs to be replaced, while an excessive reading signifies that the coil is open, and also needs to be replaced.

 

[maynerd1021]

The coil test pretty high on the secondary circuit. I replaced the coil, that reads within the suggested limits, but still have the short. I am working through continuity from the harness to the instrument cluster, but some of the wire colors are not the same as in the manual. I will report back once I find the issue.

One last question, could the points be shorting or grounding out, since the breaker only trips when they are closed?

 

[maynerd1021]

One more last question: the red and white wire comes from the alternator to the ampmeter, or does it go from the ampmeter, through the key, then to the alternator?

 

[alldodge]

The points are not the issue, when running the points ground (short) the negative side of the coil. If it was on the posative side, this would be the issue

Red from ALT thru breaker to amp meter.
Red/White to key switch
White from run side of key switch back to motor

 

[Boater31]

Since it's no longer the coil, did you try the tach as mentioned earlier? If the tach is good then I would think the only other items would be short in the other gauges, but that would only be when the key is on and the white wire is energized. Could it be a short in the alternator?