Won't start on #2 battery

[SkunkBoat]

I've been an electronics guy since 1979. I've been a teenage TV repairman. I've worked on navy gun & missle firecontrol systems. I've been a field service engineer and later a national service manager for medical diagnostic systems. I've trained tech support to troubleshoot over the phone.
Troubleshooting thru text over multiple weeks is very difficult but I will try to help
I do not know what is causing the problem. I don't know if you are missing an important symptom that has us looking in the wrong place.

in troubleshooting, much like spotting naval gunfire, there are three methods...Bracket, Ladder, and "Hunt & Peck"

You seem to be in Hunt & Peck. Thats the least effective method. Sometimes you get lucky based on a guess or knowledge of a common problem. You didn't get lucky.

At this point you will learn something by removing battery#2 from the boat, connecting the start cable from the motor directly to the positive and negative battery terminals with no other components in the circiut. If it works repeatedly then you have ruled out the battery, the motor's cables, and the motor.

From there I would use the ladder method and work in one direction, one piece at a time. from the motor thru your cabling and switches to the battery (when its in its normal position)

There is a Black Neg wire from Batt1 to batt2. I have not yet heard mention of you removing or jumping that.
Your first step in the ladder is connecting the neg of the motor cable to batt1 and using the existing neg batt1/Batt2 jumper. Then connect the pos coming directly from the motor to pos Batt2(bypass the switch). This step of the ladder tests the neg jumper from batt1 to batt2.

As you work your way thru cables (both pos & neg) look for bad connections and bad wires. Wires can be green inside and look fine from the outside. Flex them and feel for hard spots.
The bad wire can measure near 0 ohms on a meter and still drop too much voltage or fail to conduct enough current when cranking the starter.
If you have the problem, use a jumper cable to bypass the suspected cable.

 

[seasick]

The trick to tracking down these kinds of problems is to understand what causes voltage drop in a circuit and more importantly where that drop is taking place. Voltage drop is a s much a problem on returns (often incorrectly called grounds, and I too often use that term). OHM's law states that voltage is equal to resistance times current. What that means is that for a given current draw, a circuit with a higher resistance will end up with a higher voltage drop.
Many folks test for voltage relative to the battery ground ( OK, negative terminal) not realizing that there could be proper voltage with little to no load applied or there could be excessive voltage drop in a return conductor.
Components like lugs, terminal and contacts like in battery switches are all conductors and can have excessive resistance. Heck even the batteries have resistance

Let's say you have a part like a switch that has 1/10 of an ohm resistance and is connected to a draw of 2 amps which is typical for a VHF radio in receive mode. The switch will introduce a voltage drop of .1 ohm times 12 volts or .2 volts. Now lets look at a battery switch that has a resistance of 1/10 ohm but draws 100 amps like a starter can easily draw. .1 ohm time 100 amps equals 10 volts. In this case, the motor sees 2 volts (12-10) and obviously the motor wont start.
The secret to troubleshooting voltage drop issues is to measure voltage across devices and not just between the positive and negative leads. In the battery switch case, lets say you measured the voltage at the output of a battery switch and it is low. Is it low with little to no load or under heavy load. In your situation, the first thing to do is measure the voltage at the motor relative to the ground at the motor. Note that value and then crank the motor. Note the voltage again. It will be less but not a ton less. If it is very low, start working from the battery towards the motor, measuring voltage relative to the negative battery terminal. If there is excessive drop, on the positive feed, you will see it at some point. The test has to be done while cranking the motor.
If you don't see a big drop, now measure the voltage between the battery negative terminal and the motor ground while cranking the motor. You should measure a pretty small value since under load there will always be some voltage drop. If there is, you probably have a bad cable, lug or connection at the motor. All there usually is between those two test points is the battery cable. ( Well on some boats, the battery cable goes to a buss bar and from there another cable goes to the motor. You probably will only see that on hulls where the batteries are mounted forward.

The main point to stress is that just measuring the voltage without any load is not a good test to find excessive voltage drops.

In the case of a bad battery switch, if you measure the voltage at the input lug to the output lug ( basically you are measuring voltage across the switch contacts under load) you should see just about zero volts, perhaps a few millivolts). If that is what you get, the switch itself is not bad.

 

[Fishtales]

Check your grounds as well as positive lines.

 

[Pighunter]

What battery switch did you get?

I bought a Perko from west marine.

 

[Blaugrana]

I bought a Perko from west marine.

Ok assuming you did a likefor like replacement with Off, 1, 2, both.

I would follow the advice given here, you need to start segmenting and isolating the circuits to ensure all hops work. Start with making sure the batteryis good like skunkboat says and then go from there methodically ruling out the cables.

Have you done a schematic yet of your circuits? This would help with troubleshooting

 

[Blaugrana]

I've been an electronics guy since 1979. I've been a teenage TV repairman. I've worked on navy gun & missle firecontrol systems. I've been a field service engineer and later a national service manager for medical diagnostic systems. I've trained tech support to troubleshoot over the phone.
Troubleshooting thru text over multiple weeks is very difficult but I will try to help
I do not know what is causing the problem. I don't know if you are missing an important symptom that has us looking in the wrong place.

in troubleshooting, much like spotting naval gunfire, there are three methods...Bracket, Ladder, and "Hunt & Peck"

You seem to be in Hunt & Peck. Thats the least effective method. Sometimes you get lucky based on a guess or knowledge of a common problem. You didn't get lucky.

At this point you will learn something by removing battery#2 from the boat, connecting the start cable from the motor directly to the positive and negative battery terminals with no other components in the circiut. If it works repeatedly then you have ruled out the battery, the motor's cables, and the motor.

From there I would use the ladder method and work in one direction, one piece at a time. from the motor thru your cabling and switches to the battery (when its in its normal position)

There is a Black Neg wire from Batt1 to batt2. I have not yet heard mention of you removing or jumping that.
Your first step in the ladder is connecting the neg of the motor cable to batt1 and using the existing neg batt1/Batt2 jumper. Then connect the pos coming directly from the motor to pos Batt2(bypass the switch). This step of the ladder tests the neg jumper from batt1 to batt2.

As you work your way thru cables (both pos & neg) look for bad connections and bad wires. Wires can be green inside and look fine from the outside. Flex them and feel for hard spots.
The bad wire can measure near 0 ohms on a meter and still drop too much voltage or fail to conduct enough current when cranking the starter.
If you have the problem, use a jumper cable to bypass the suspected cable.

Thinking through your advice. If engine starts on the other battery, then does that mean the motor cables are good? So once we know the 2nd battery is good, would jumping the two cables on the 2nd battery be the next step? If it starts, then one of those cables are bad.

 

[seasick]

Thinking through your advice. If engine starts on the other battery, then does that mean the motor cables are good? So once we know the 2nd battery is good, would jumping the two cables on the 2nd battery be the next step? If it starts, then one of those cables are bad.

That's logical. If the motor starts on one battery but not the other, the problem could be a bad cable between the switch and battery that has issues. It could also be a bad jumper cable that bridges the negative terminals on the two batteries.
It is less likely but still possible that there are more than one out of spec voltage drop areas and added up, the motor doesn't have enough voltage to start

 

[Pighunter]

I'm not ignoring you guys I'm just muddling my way through this. I'll post updates as they develop.

 

[seasick]

I'm not ignoring you guys I'm just muddling my way through this. I'll post updates as they develop.

That's OK, we're just rambling on

 

[Fishtales]

Can always swap the batteries to start to eliminate components.

 

[seasick]

sometimes swapping batteries is a big chore. I prefer to find out what the problem is first before swapping parts, especially heavy bulky ones. If possible it is easier to swap the positive battery cables and see what difference that makes ( It make not any difference if the problem is a bad ground wire or connection)

 

[SkunkBoat]

ya troubleshooting battery systems "in place" using a set of jumper cables first is great if you have a clear sense of what you are trying to accomplish.
I find taking voltage measurements in this case can be inconclusive or misleading.

But there is a lot to be said for removing everything once in awhile, holding the pieces in your hand and looking at them, putting it back together with good stuff...
Especially if you have a boat that is new to you or you have not done it since that last battery change.

 

[seasick]

As I age, batteries and other parts just seem to get heavier. A jumper cable is a lot lighter.

 

[Pighunter]

As I age, batteries and other parts just seem to get heavier. A jumper cable is a lot lighter.

I agree, also the port side battery does not have an easy egress. When I installed the new batteries last June I had the live well out and it made it a lot easier.

Biggest problem right now is I'm spread way to thin. I've got way to many projects going at the same time. I used to think how nice it will be when I retire with all my extra time. HA I'm busier now than when I had a job.

 

[Blaugrana]

I agree, also the port side battery does not have an easy egress. When I installed the new batteries last June I had the live well out and it made it a lot easier.

Biggest problem right now is I'm spread way to thin. I've got way to many projects going at the same time. I used to think how nice it will be when I retire with all my extra time. HA I'm busier now than when I had a job.

Do you have an OX66? I used to think taking the port battery was near impossible to take out and not worth the effort. However, a few folks explained how to do it and I can remove it in mins. No disconnecting the oil tank or anything.

Let me know if you need help on how best to do it.

 

[seasick]

One check I didn't emphasize enough is a bad cable end, either corroded and/or loose. If the battery cable ends have heat shrink on them, it can be hard to tell if the connection is good. Tug and pull hard to look for problems.
As mentioned, if connections are bad, that will cause voltage drops under load

 

[Fishtales]

Many times it is a connection, corrosion or wire problem. Swapping to isolate requires these be broken and inspected and come for free with the work and it generally is free and simple. I take strategic advantage when I can.

 

[Pighunter]

Do you have an OX66? I used to think taking the port battery was near impossible to take out and not worth the effort. However, a few folks explained how to do it and I can remove it in mins. No disconnecting the oil tank or anything.

Let me know if you need help on how best to do it.

Yes a 225 hp ox66