Feb 27, 2002 - Atomic 4 - Starting-Circuit and Charging-Circuit Service.


My friend, Dan Rickert, is an automotive repair pro. He runs his own business up near Lake Amador, CA. Last summer, at the Cruiser Challenge in Montery, he offered to drive to the SF Bay area to check out the starting and electrical system on Bijou's Atomic-4. He's a man of his word; two weeks ago I got a call saying he could come visit for a weekend and work on the boat.

He inspected the whole starting circuit, plus performed some simple tests on the alternator. The following are my notes on what he did. I think I understood most of what he taught me, but I'm just a beginner when it comes to understanding starting circuits. So if there are errors here, it's probably my lack of complete understanding, and not a negative reflection of Dan's expertise.


A little history

We had trouble starting the engine in 2003, but it went away for a while after my mechanic replaced the ignition switch. It always ran smoothly -if it started. Sometimes it roared to life immediately when we turned the key. Sometimes, it was completely dead when we turned the key; it didn't even try to start.

We had trouble again with starting the engine last spring (2004). It was the same story: It always ran smoothly -if it started. Sometimes it roared to life immediately when we turned the key. Sometimes, it was completely dead when we turned the key; it didn't even try to start. So I cleaned and replaced the connections on the ground circuit from the battery to the engine block. I cleaned the connections on the solenoid and ignition switch, which had been replaced. The engine started without fail for the rest of the 2004 season, but I knew we had a problem lurking somewhere in that old wiring.


Preface to tests and repairs:

The starting circuit was tested under "cranking" (estimated by Dan at 50-100 amps) in order to find resistance. You won't find bad connections in a starting circuit with small current loads. While we were testing the starting circuit, we kept the TruStat charge connected to both batteries. With the charger connected, the battery voltage was 13.4 v.

Dan explained to me that the 13.4 volts was due to surface charge on the plates from the charger, and if the batteries were good, it would equalize down to 12.4 in 20 minutes if we disconnected the charger.

For the cranking load tests, Dan removed the wire from the coil at the top of the distributor and grounded it to the engine block. This was to prevent the engine from starting. We kept the fresh water intake closed during cranking to prevent flooding the cylinders.

For the tests of the alternator, Dan turned off the TruStat battery charger, reconnected the coil to distributor wire, and started the engine.


1. Main engine ground circuit: negative post on battery to engine block (black, 4-gauge AWG):.

Before cleaning and , the voltage drop was 0.7 volts under cranking load. After cleaning it was 0.3 volts. Dan inspected and cleaned the negative battery terminals and wires connected to the negative terminals. Installed neutralizing/anticorrosion pads on negative battery terminals, and dielectric grease. Replaced one of the heavy duty 1/4" ring-terminal for 4-gauge wire on one cable because it was corroded beyond acceptable standards. Installed star washed under 1/4" nut on other end (engine block). Cleaned and gooped smaller ground wires (black) to negative ground bus (for existing bilge pump and old vhf radio circuits, which are wired directly to the battery with their own fuses and do not go through the main circuit panel).

Also cleaned and treated the positive connections to to the positive terminals on both batteries from the TruStat charger.

. Positive side of battery to positive terminal of solenoid (the thick red cable on solenoid) .

There are three components in the positive side of the circuit:

Before cleaning connections at the battery, the voltage drop between the positive post on the #2 battery and the positive terminal on the solenoid was between 1.5 and 2.0 volts under cranking load (more than 0.5 volts average per component) . That's indicative of high resistance.

He started by servicing the ends of the circuit, since they were more easily accessed than the battery switch. He cleaned and installed neutralizing pads and dielectric grease on both positive battery terminals, which were corroded from hydrogen generated while charging. Inspected the positive connection at the solenoid and it was in very good conditions, because I had cleaned and replaced it 3-4 months ago.

After servicing the connections at both ends of the circuit, the voltage drop improved only to 1.17 volts, indicating there was still high resistance at the connections on the back of the battery selection switch or within the battery switch itself.

Dan serviced the connections on the back of the battery selection switch. After servicing the connections at the battery selection switch, the voltage drop was reduced to a total of 0.6 volts across the whole circuit, at full cranking power.

A voltage drop of only 0.6 volts over the whole positive side of the circuit is very good. It's an average drop of only 0.2 volts for each of the three components in the positive side of the starting circuit

(Prior to cleaning and servicing, the total voltage drop in the negative and positive sides of the circuit was 0.7 v + 1.5 v = 2.2 v. That means that with a fully charged battery at 12.4 volts, only 10.2 volts was reaching the solenoid and starter at full cranking power of 50-100 amps. According to Dan, that was pretty marginal and any further corrosion might have caused enough additional resistance to get the starter cranking. He said you usually need at least 10 volts at full cranking amperage to get the starter engaged and turn the engine over.)


3. Ignition switch (terminal labeled"BATT) to positive terminal on solenoid. Initially, the voltage drop was 1.5 volts under cranking load. After replacing the wire, the voltage drop was reduced to less than 0.5 volts.

Dan took a look at the wiring and noted that the #10 wire (red) was 10 or 20 feet long, coiled up in the OEM wiring harness. He thought that was inappropriate to have such a long wire to connect two things that were less than 2 feet apart.

Dan checked the plug connectors in the harness; they looked clean and good (I had cleaned them twice in the past two years)

Dan installed 2' of new red 10 gauge marine graded Ancor wire (with Ancor connectors) between the ignition switch and the solenoid. He left the old wire in the harness connected in parallel. Dan said that 10 gauge wire was required, because he estimated that the amperage on that part of the circuit was between 15 and 30 amps.

Dan tested the voltage drop between the ignition switch and the solenoid after replacing the wire. The voltage drop was reduced from 1.5 volts to less than 0.5 volts (my notes are incomplete here, except to note that less than 0.5 amps was acceptable and 0.3 was good.)


4. Checking the alternator output.

Basic tests showed the alternator and regulator were working properly. Output is sufficient to quickly recharge the battery after starting and simultaneously run nav lights, blower and instruments.

Without additional testing equipment, Dan can't tell me what the maximum output the alternator is actually putting out.

The alternator was replaced by the previous owner in 2001. It has about 100 hours on it. Dan noted that it looks like new, but might have been professionally rebuilt.(I think Dan told me it was a 50 amp alternator, but I'm not sure. I'll have to read the label on the alternator next time I'm back at the boat)

We disconnected the shore power charger, (so the surface charge on the battery plates would dissipate and equalize) reconnected the distributor, and started the engine.

Dan wanted to do a load test, so he asked me to turn on everything I could that was DC powered. I turned on the cabin lights, engine compartment blower, and all the cabin lights. (The nav lights and instruments are not yet rewired). The alternator was putting out 5-6 amps with that load, with the engine running at idle speed of about 600 rpm. The output remained constant when we increased the revs to about 1100 rpm.

According to Dan, that's appropriate output for the current load we were drawing, and indicated the alternator was performing correctly at that load. (He said he didn't bring test equipment for high load testing, so these tests were the best he could do)

Then he checked the voltage across the battery terminals and at the alternator. The voltage across the battery 13.2 volts with a fully charged battery. The output was 13.8 volts at the alternator, which he said was very good. Voltage was steady as we increased revs from 600 rpm to 12,000 rpm.

Dan said the output of the alternator was more than sufficient to recharge the battery after starting, and to run loads like cabin lights, nav lights, instruments, etc. Without further testing, he couldn't say if it would be sufficient to run heavy loads (like turning on everything at the same time: our electric cooler, stereo, instruments, cabin and nav lights, etc.)


Post words:

After I serviced the "ground side" of the starting circuit last summer, the Atomic 4 started every time we turned the key. But even though the engine started from that time forward, it worried me that I didn't know how many more problems there might be lurking in the system. Dan's "service call" revealed that I had every reason to worry.

There was enough voltage to start the boat when the battery was charged to 12.4 volts, but just barely enough. Dan's testing showed that the bad connections in the wiring left the voltage just barely above the threshold, with little safety margin for further corrosion as time passed.

With the repairs he made, we now have a comfortable margin of safety, and the starting circuit should be trouble free for at least two years or longer, even in a marine environment..

However, I plan to inspect and clean the connections, and test all the legs of the circuit, at the start of every season from now on. Now I am familiar with the circuit, and I know how to check the voltage at each leg of the circuit and components.

If one component should fail at some future time, I will be able to identify it and fix it.



We got to the boat at about 10:30. Dan tested everything, made a trip with me to the chandlery to pick up a few supplies and got everything in Bristol condition in short order.

By 1:30 pm,. we were sitting in the pub at Quinn's Lighthouse for lunch and a beer, chatting and laughing as we had a beer and ate lunch, enjoying the view of the boats on the Estuary.

My husband and I thoroughly enjoyed his company for two days. Dan is a delightful companion and a good man. He's funny and can converse intelligently on a myriad of topics. He even cooked a fabulous Thai meal for dinner before he left!

This man is a SAILOR, he can COOK and he can FIX BOATS! And he's a genuine nice guy to boot! .... If he weren't already happily married, I'd fix him up with one of my girlfriends!

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