CONTINUOUSWAVE

Starting my 2017 Mercury VERADO outboard engine has become a problem. Here is a narrative of the problem and attempts to solve the problem.

The engine cranking batteries are five years old. The batteries are rated to be able to deliver 1,000-Amperes (when the temperature is above 32-degrees-F, or the marine-cranking Ampere rating or MCA).

Following a four-month period of non-use of my boat and in May of 2024, I attempted to start my 2017 Mercury VERADO outboard engine. The speed at which the engine was cranking over sounded like it was slower than normal, as if the voltage provided by the cranking battery (or bank of batteries) was lower than normal.

I decided to replace the batteries with new batteries, even though the old batteries appeared to be at a state of charge of "full" and the batteries "took" a load.

After installing new batteries to replace the old batteries, the engine starting speed continued to be slower than normal.

I then check the connections at the solenoid [relay that control current to the starter motor in the VERADO engine]. I was able to tighten the retaining nut slightly. The VERADO engine was then able to be cranked "up" and I considered that I had solved the problem with the slow engine cranking speed.

On the next day before noon, I checked the voltage at the battery terminals, at the battery switch, at the bus bar downstream of the battery switch, and all showed "good" voltage and "load tolerance."

If and when I would connect an external battery charger to either battery [apparently there are two batteries in the bank used for engine cranking] and set the mode on the external battery charger to "START", the VERADO engine will crank "right up."

On that basis I assumed I was putting more than 1,000-Amperes to the starter motor. This leads me to believe that the actual cause of the problem with cranking speed being too low is with either the starter motor or the solenoid relay.

Give me advice on this problem.

Any advice given will be appreciated.

From your narrative my inference is that the problem you are having is that in attempting to start your outboard engine the speed of the cranking motor seems to be too slow. You do not actually indicate if the engine is able to start or not when this slow cranking occurs. To know if the engine actually starts with the slower cranking speed would be useful.

Also, you frequently refer to the battery cranking the engine in the plural. It is not clear in your narrative if you were using just one battery at a time to attempt to start the engine or if you were using two batteries in parallel to attempt to start the engine. To know if your remarks apply to just one battery or to a bank of two batteries in parallel would be useful.

As for your initial suspicion that the cause of the slow engine cranking speed was caused by a bad battery, I would agree that that is a good first analysis. After many years or working with electrical devices which are powered by a storage battery, I have developed a general rule:

If a device that is powered by a storage battery does not operate properly, the first component to check is the storage battery.

After you discarded the five-year-old batteries and replaced them with new batteries, and the problem with slow engine cranking speed during starting continued, it is probably reasonable to assume that the cause of the problem was not in the battery or batteries you discarded. However, depending on the climate and use of a battery, and on the initial quality of the battery, and the care given to the battery to maintain it a a high state of charge, a service life of only five years is not particularly awful. Replacing the old batteries may have been a prudent step, even if they were not the actual cause of the slow engine cranking during starting.

The FIRST step you should have taken was to measure the terminal voltage at the batteries terminals with a high-accuracy digital voltmeter, and to record the terminal voltage when there was no load on the battery, and then to record the terminal voltage when the battery was attempting to start the engine.

To know those two voltages would have been useful in assessing the condition of the those batteries and whether or not they were the cause of the slow cranking speed during starting attempts.

The SECOND step you should have taken was to measure the voltage at the OUTPUT terminal of the solenoid relay during engine cranking. Then to compare the two voltages--at the battery terminal and at the solenoid output terminal--to assess how much voltage DROP was occurring in the positive portion of the circuit.

The THIRD step you should have taken was to measure the voltage at the negative terminal of the battery to the negative terminal of the main battery cable where it attaches to the engine block. This voltage would be the voltage drop occurring in the negative portion of the circuit.

There are many elements of the battery circuit and the engine starter motor to consider as possible locations for bad connections. See my article on precisely this topic for a list of places to look for bad connections. Read at

Engine Starting Circuits
https://continuouswave.com/whaler/refer ... Start.html

In the HIGH CURRENT section of the circuit there are 20 places where a poor electrical connection could occur.

A problem in finding bad connections in low-voltage circuits is they may appear to be fine by eye. Bad connections generally can be found by measuring the voltage drop across their leg of the circuit. All measurements of voltage drop must be made while the load of the engine starter motor is applied.

If you need more instructions on how to measure the voltage drop in a complex circuit by measuring the voltage drop from one section to another, let me know and I will explain in more detail.

Jim, many thanks for your thorough response. I will get to work on the steps you have provided and report back with my findings with more specificity.

Jim, to answer your questions:
Step one - Batteries. All good - 13.3 volts on both, with load 12.8


Where the concern appears to be:
(The SECOND step you should have taken was to measure the voltage at the OUTPUT terminal of the solenoid relay during engine cranking. Then to compare the two voltages--at the battery terminal and at the solenoid output terminal--to assess how much voltage DROP was occurring in the positive portion of the circuit.)

Input side of solenoid - 14 volts
output terminal of solenoid during engine cranking - 8 volts.

I replaced the solenoid and the problem still exists.

Thoughts?

WAIT--UNDER REVISION--DON'T READ YET

Kapharms wrote:--Input side of solenoid - 14 volts
--Output terminal of solenoid during engine cranking - 8 volts.

I replaced the solenoid and the problem still exists.

Thoughts?

I have to ask for a bit more detail: when you measured 14-Volts at the input side of the solenoid relay, was that also while the engine was cranking?

Let me see if I can add more understanding. We are looking for the portion of the circuit which has a big voltage drop occurring WHILE THE ENGINE IS BEING CRANKED OVER. We start at the battery positive terminal and proceed toward the starter motor. I will make a table of reference designations so I can illustrate better

A = battery positive terminal
B = input side of starter motor solenoid (this will include any battery switch that is in the circuit between A and B)
C = output side of the starter motor solenoid
D = starter motor positive terminal
E = engine chassis
F= battery negative terminal

The circuit path is A---->B---->C---->D---->E---->F.

An accurate voltmeter that can measure to at least 0.1-volt resolution is used. The negative lead of the voltmeter is connected to F.
The positive lead is moved in sequence from A to B to C to D while the engine is being cranked. You can stop cranking the engine while moving the test probe between locations.

What you will be doing is measuring the following voltages; I also mention which circuit elements are involved:

A = the battery terminal voltage under load during cranking; no circuit elements involved, only the battery and its internal components

B = the voltage available at the starter solenoid input under load; all wiring, connection, switches, fuses and so on from battery terminal to solenoid

C = the voltage available at the starter solenoid output under load; includes the internal contacts in the solenoid

D = the voltage at the starter motor positive terminal; includes the wiring from solenoid to starter motor.

E = the voltage at the engine chassis; the only circuit element left is the main negative lead between engine chassis and battery negative terminal; this can also cause a significant voltage drop.

Then we want to compare the voltage readings B, C, D, to the voltage at A, all measured during cranking.

When a heavy load is imposed on the battery, the terminal voltage (A to E) will tend to sag from the resting voltage around 12.5-Volts (or higher) for a battery at a full-charge state) to a lower voltage, but generally not below perhaps 10.5 to 11.0-Volts if the battery has sufficient reserve power.

The voltage at B should be very close to the voltage at A; the added circuit elements are connectors, wiring, a battery switch, perhaps a fuse; the voltage decrease should be minimal, perhaps 0.2-Volts or so.

The voltage a C should also be very close to the voltage at B, a the only circuit element is the internal contacts of the solenoid. Again, a drop of 0.2-Volts would not be unusual, but the less drop the better.

The voltage a D should again be very close to the voltage at C, indicative on very little voltage drop in the connectors and wire that connect the solenoid to the starter motor positive terminal.

The voltage at E should be very small, not more than 0.5-Volts; any sign of a significant voltage between the engine chassis and the battery negative terminal indicates a poor connection in the main battery cable that runs from the engine chassis to the battery negative terminal, which can very well be part of the problem.

What should be observed is that most of the voltage sag occurs in the battery, and as the current flows to the starter motor from the battery and passes through the various elements of the circuit, there is no unusually large voltage drop occurring.

Your report of 14-Volts at B and 8-Volts at C suggests the solenoid contacts were bad. But I think you were not measuring both times during cranking. Please comment on that.

Also, you keep the Voltmeter negative lead always connected to the battery negative. You probably will need to extend the battery negative to reach the Voltmeter lead by adding several feet of extension. As long as the extension cable is firmly connected, you do not have to worry about resistance, as the current flowing to the Voltmeter is very small.

Here is what I just recorded:

A = the battery terminal voltage under load during cranking: 12.2 volts while cranking

B = the voltage available at the starter solenoid input under load: 8 volts while cranking

C = the voltage available at the starter solenoid output under load:8 volts while cranking

D = the voltage at the starter motor positive terminal: 8 volts while cranking

E = the voltage at the engine chassis: I am uncertain how to test this.



Compare the voltage readings B, C, D, to the voltage at A, all measured during cranking.
There was a 4.2 volt drop from the battery terminal to B,C and D while cranking

I disconnected the main positive cable where it connects to the terminal on the motor. I then connected a set of jumper cables from the battery to the incoming terminal that I had just removed the battery cable from--meaning that in essence I replaced the positive battery cable with a jumper cable. I connected a jumper from the battery negative to the engine ground terminal. It Started right up, Voltage dropped from 13.3 to 12 volts while cranking.

I believe the voltage drop is being caused by a bad positive cable from the bus bar to the motor. Not certain how to test the negative cable. I may just replace both as a precaution.

Clean the battery cable fittings at the battery, the battery switch terminals and the engine

Clean the positive and negative posts at the engine and battery switch with a wire brush.

Retest voltage.

Kapharms wrote:Here is what I just recorded....

Thanks for the new data.

You diagnosis is correct: the source of the voltage drop appears to be in the segment of the circuit from the battery terminal, through the battery switch, through any connections in that path, through the main engine cable, to the solenoid.

You should check all the connections and fittings involved. Loosen and clean all connections. To clean a connection use WD40 as a cleaning fluid, and use very fine emery paper, say 600-grit or higher, to removed any oxidation from the ring terminal connectors or binding post. NEVER USE A WIRE BRUSH. Use a an old toothbrush with WD40 to clean threaded posts, scrubbing as needed. Or use a stiff brush with nylon bristles. Creating scratches in electrical connections just invites more corrosion to form. Terminals are tinned to protect the underlying copper from oxidation. Do not scratch off the tin surface with a wire brush.

Regarding how to measure the voltage from the engine chassis to the battery negative, the method is the same as for the other points. The Voltmeter negative probe connects to the battery negative terminal post, and the Voltmeter positive probe connects to the engine chassis at the stud where the negative cable is connected. Any voltage measured between those two points is the voltage drop occurring between the engine chassis and the battery negative. You might assume there would be no drop, but during cranking a large current flows, so even a small resistance will cause a voltage drop. If there is any significant voltage drop in the chassis to battery negative terminal, you need to check all of those connections.

Do you have a main battery switch? If you do, measure the voltage between the battery terminal on the switch and the common terminal on the switch during cranking. It is quite possible that the switch is causing a significant voltage drop.

One other thing to consider is the ring terminal connections to the cable itself. These are usually crimped to the cable end with a compression type swaging tool or some kind of machine that replicates the tool. If the crimp on the ring terminal is not sufficiently tight a voltage drop will occur. In some cases the ring terminal will become hot or melt the cable insulation. All this is hard to see or feel. Replacing the cables is a good plan and checking the tightness of the ring terminal crimps before installation is recommended.

I give a list of 20 possible connections in the high-current engine starting circuit that could cause trouble in an article in the REFERENCE section at

Electric Starting Circuits
https://continuouswave.com/whaler/refer ... Start.html

The list does not include a primary power disconnect switch, so if your boat has a switch in the engine starting circuit, you need to check all of those connection points, too.

REPORTING BACK
The root cause of the problems [with the engine cranking] has been found.

jimh wrote:I give a list of 20 possible connections in the high-current engine starting circuit that could cause trouble in an article in the REFERENCE section...

As per jimh's suggestion, I inspected all 20 possible connections in the high-current circuit, as well as all terminals in the primary power disconnect switch. Every indication was the [source of the voltage drop was in the] main positive and negative cables running into the engine.

As I was attempting to pull through new [battery cables] into the flexible rigging tube [that carries all the cables and hoses to to the engine cowling fitting], but nothing would budge. Eventually I determined the the fuel hose (that was also in the flexible rigging tube] had a pin-hole leak that had been spraying fuel, albeit a small amount, on all of the other cables in the flexible rigging tube. (See Figure 1, below.)



Every cable in the rigging tube experienced some level of degradation as the tube had no weep holes-- a bad design.

After replacing all the cables and hoses, including a new fuel hose, the engine now starts and runs like a champ. Also, I also replaced the solid rigging tube with a mesh version.

Many thanks to all for the help in finding the cause of this problem.

Thanks for the follow-up giving us the cause and the remedy for the problem of poor engine cranking. Your illustration in Figure 1 is also very nice.

Judging from Figure 1, the inside diameter of the flexible tubing that carried the battery cables, fuel hoses, and other cables was rather undersized, as the closed-wall flexible tube looks like it was crammed full of too many hoses and cables. The cables were probably abrading against each other or against the inside wall of the flexible tubing, which may have been the cause of the pin-hole fuel leak.

Unless the gasoline fuel leaking out in the flexible rigging tube was being completely absorbed by the insulation material on the other cables, I would have thought the fuel would have been slowing running back down the flexible tubing and collecting in the boat. Generally gasoline has a quite noticeable odor, and I would have expected that you could smell the presence of the leak.

Also, I expect the engine fuel efficiency will improve not that fuel is not being lost, which is another benefit from fixing the original problem.

Good outcome for both the battery problem and possible future problems as the other cables began to decay more.