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Author Topic:   Mercury Stator Preventive Maintenance
turkeycreektrout posted 04-30-2008 09:17 PM ET (US)   Profile for turkeycreektrout   Send Email to turkeycreektrout  
Hello. I just replaced the stator, trigger, and switch box on my 1989 Mercury 80-HP motor. I have read where this has been a big problem for the mercs and after spending $760 I just want to make sure I am doing everything I can to avoid it again. Now that all this has been replaced, is there anything I can do to keep it from happening again?

The motor itself is in great shape, and I just bought the Skeeter boat few weeks back. The previous owner took it out maybe two three times a year. I have a Walmart EverStart marine cranking battery; is this okay? This is my first bass boat and i am excited about using it for a couple of years until I can get a new one. Thanks for your help and good luck on the water. Sean

jimh posted 04-30-2008 11:09 PM ET (US)     Profile for jimh  Send Email to jimh     
Don't use wing nuts on your battery connection.

Don't operate the boat in such a way that the motor has a chronic high-current charging load. The charging system is probably not rugged enough to put out full rated charging current all the time without overheating and failing.

jimh posted 04-30-2008 11:11 PM ET (US)     Profile for jimh  Send Email to jimh     
Check your battery terminal voltage to verify that you don't have a shorted cell.
Henry posted 04-30-2008 11:21 PM ET (US)     Profile for Henry  Send Email to Henry     

What do you mean by a "chronic high current charging load"?

jimh posted 04-30-2008 11:41 PM ET (US)     Profile for jimh  Send Email to jimh     
Chronic = all the time
High-current = close to the maximum rating of the charger

If you operate the boat in a manner where the battery is chronically in a state of deep discharge, the motor will always be trying to deliver high current to it. The motor might be rated for, say, 20-Amperes of charging current, but I get the feeling that it can't deliver that kind of current all the time without causing something to overheat.

In the 1980's when that Mercury charging circuit was designed, the designer probably did not anticipate that the motor would be asked to deliver the full rated charging current all the time. In most situations a motor starts, and it only has to deliver a few amperes to recharge the starting battery back to full-charge float voltage. If you operate a lot of electrical loads and drag the battery voltage down all the time, you will be asking the motor to chronically recharge it at high current.

turkeycreektrout posted 05-01-2008 06:30 AM ET (US)     Profile for turkeycreektrout  Send Email to turkeycreektrout     
[H]ow would [I] know if [I] had a shorted battery cell? [W]hat would be the voltage?
jimh posted 05-01-2008 10:52 AM ET (US)     Profile for jimh  Send Email to jimh     
A nominal "12-volt" battery has six cells. When at full charge they each have a cell voltage of about 2.2 volts. If one cell is shorted, there will only be five cells:

5 X 2.2 = 11-volts

This is often enough voltage to crank over an engine.

What destroys most solid-state electrical component:


--voltage transients

WhalerAce posted 05-04-2008 10:03 PM ET (US)     Profile for WhalerAce  Send Email to WhalerAce     
I gotta ask:

What is wrong with wing nuts? Not just finger-tight, I understand, but other than that possiblitiy, what is your objection?

My prefer wing nuts (I still tighten them with vise-grips) because in an emergency situation, you can still loosen the battery conections, whereas you need two separate wrenches if you just use normal nuts (nuts are usually two different sizes).

Just curious.

--- WhalerAce

Chuck Tribolet posted 05-04-2008 10:40 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Whaler Ace: You just need one wrench, because the other side
is usually tapped into the bit that clamps on the battery.

But I do agree that there's nothing wrong with an
appropriately torqued wing nut. In a pinch (problem), I can
find something to loosen a wing nut faster than a hex nut.
Other than that, if it works, it works.

Six cells working = 6*2.2V = 13.2V. MMM, I think my truck
has a dead cell.


jimh posted 05-05-2008 09:20 AM ET (US)     Profile for jimh  Send Email to jimh     
There is nothing intrinsically wrong with using wing nuts as part of an electrical connection. In electrical terms they are as good as another steel fastener or retainer.

If you read the manufacturer literature on engine installation you find prohibitions against using wing nuts for the battery connections. The exact reasoning or motivation for these prescripts is not given.

I make the inference that the prohibition against using wing nuts as fasteners in electrical connections for the primary battery distribution on small boats is for a simple reason: then tend to become loose because they were not sufficiently tightened. A loose connection causes sparking and interruption of the current flow in the circuit. The battery is connected to the outboard motor charging system. The charging system contains inductive elements in which energy is stored in the magnetic field surrounding the inductor. When such a circuit is broken, the magnetic field surrounding the inductor collapses, inducing a voltage. The voltage is proportional to the rate of change, and since the disconnection of the battery is instantaneous, the rate of change is high, and thus the voltage can be high. These transient high voltages generated are called high voltage transients. When the battery is connected to the electrical system of the motor, the battery provides not only a source of power but represents a very low impedance which is shunted across the entire system. It is extremely difficult to develop a high voltage across a low impedance. When the battery is disconnected, its low impedance is removed from the electrical system and the impedance of that system rises, making it easier for high voltage transients to be generated.

Previously I mentioned that one of the primary causes of failure in solid state electrical devices is high voltage transients. Therefore, I make the following inferences in this sequence:

--wing nuts tend to produce loose connections
--loose connections cause high voltage transients
--high voltage transients damage solid state electronics

The manufacturer of an outboard motor is in the position of providing a warranty against failure of the solid state electronics in the motor. I believe that manufacturer has come to the conclusion that one way to reduce the frequency of failure of their products is to specify that wing nuts must not be used to connect to the battery.

The wing nut has been designed with the intention of being tightened by hand. As far as I know, there are no specialty tools for tightening wing nuts. While it is possible and it has been proposed that various tools be applied to tighten a wing nut, it seems rather odd to choose a wing nut as the fastener if you are going to tighten it with a tool anyways. If you want to use a fastener which you are going to tighten with a tool, there are far better choices than wing nuts. The standard hex nut is much more easily tightened with much more common tools.

bigjohn1 posted 05-05-2008 08:24 PM ET (US)     Profile for bigjohn1  Send Email to bigjohn1     
I have used wing nuts on every boat I have owned over the years with no problems. Just use an appropriate (insulated) tool to tighten them properly and not just your fingers. A valid point is made though on voltage transients potentially damaging electronic components. Here is food for thought though, I personally use insulated needle-nose pliers for tightening my battery wing nuts and have never shorted anything. If I use hex nuts on my battery posts, I have two (proper) choices of tools to use: a socket and ratchet, or an open-end or box wrench. Since many ratchets and wrenches are un-insulted, you run the same risk of introducing the very problem you are trying to avoid – a voltage transient or worse, a short. This happens when the 6-10” ratchet or wrench unintentionally contacts the opposite battery post during nut tightening.

Wing nuts and insulated tools for me.

jimh posted 05-05-2008 08:53 PM ET (US)     Profile for jimh  Send Email to jimh     
If you are seriously concerned with the possibility of shorting something out while tightening the hex nut fastener on a battery terminal, you can buy a box-end wrench of the appropriate size and wrap it with SCOTCH 33-Plus vinyl electrical tape. One layer of tape is good for several hundred volts of insulation, so a layer or two of tape will be adequate insulation.

I am sure you can buy a suitable box end wrench for less than $10. Or, use $0.25 worth of tape on an existing wrench, then remove it when finished.

A box end wrench is much less likely to slip off a hex nut fastener than a pair of pliers on a wing nut.

bigjohn1 posted 05-06-2008 12:42 AM ET (US)     Profile for bigjohn1  Send Email to bigjohn1     
This is a classic case of you do it your way and I’ll do it my way. I like my way as it has worked just fine for many, many years now. There is often more than one “right” way of doing things and this appears to be just such a case.
jimh posted 05-06-2008 10:09 AM ET (US)     Profile for jimh  Send Email to jimh     
Yes, your way, my way, then there is always the manufacturer's way, and if you use wing nuts you probably will not get warranty coverage if you have a problem.

I love wing nuts. There is a little gate on my bird feeder that uses wing nuts to adjust the amount of seed that falls out. Very handy to adjust it without a wrench. Wing nuts are perfect for some applications.

Do you use wing nuts on your car battery, too?

knothead posted 05-07-2008 01:51 PM ET (US)     Profile for knothead  Send Email to knothead     

I don't use wingnuts on any of my batteries. I just seem to date them.


bigjohn1 posted 05-08-2008 09:16 AM ET (US)     Profile for bigjohn1  Send Email to bigjohn1     
It would be nice to see a pointer to where hex nuts are a manufacturer's requirement on a 1989 Mercury 80-HP outboard motor.

I did a bit of searching and see that Mercury dictates the usage of nuts on the VERADO and OPTIMAX lines, none of the other lines though. I also checked the Honda outboard site and see no direction to use hex nuts on ANY of their outboards up to 225hp. I started to search Yamaha's site and lost interest.

Hex nuts would be ideal on a 1989 Mercury 80-hp outboard but are by no means a manufacturer's requirement.

seabob4 posted 05-08-2008 09:10 PM ET (US)     Profile for seabob4  Send Email to seabob4     
You are correct. Verados REQUIRE hex nuts and lock washers. Optis, I don't think so. But the point of this whole discussion is the proper maintenance of one's electrical system, regardless of accessories, electronics, or what. A lot of these Whalers are old boats, and thus, their wiring needs to be replaced, period. As well as switches, breakers/fuses, etc.
jimh posted 05-09-2008 08:34 AM ET (US)     Profile for jimh  Send Email to jimh     
Here is an excerpt from the rigging instructions for Bombardier Evinrude outboard motors:

"IMPORTANT: Do not use wing nuts to fasten
ANY battery cables. Wing nuts can loosen and
cause electrical system damage not covered
under warranty."

davej14 posted 05-09-2008 10:52 AM ET (US)     Profile for davej14  Send Email to davej14     
This question of using wingnuts vs hex nuts on a battery terminal is always good for a debate. I see no reason why a properly tightened wing nut is any less reliable or more likely to loosen than a similarly tightened hex nut. In either case, hand tightening is not sufficient. I like the ability to make this connection without a specific tool. I have been boating for 30 years and have personally never used anything but wingnuts without incident.

For a motor manufacturer to specify hex nuts as part of their warranty requirements crosses the line in my opinion. Now if they specify a torque requirement, that would make more sense and would necessitate the use of hex nuts. On the other hand, I would not want to be required to read a torque wrench when I tighten the battery terminals in my console. I would not be able to get my head into position to see the readout.

Bottom line is use what you are comfortable with but make sure they are tight.

Whale1 posted 05-09-2008 11:01 AM ET (US)     Profile for Whale1    
Based on previous good advice postings I have changed over to hex nuts from wing nuts on my battery and I check their tightness before each trip.

Every boat trouble shooting article I have read recommends that you carry some tools on board, at least a pair of channellock pliers and a Leatherman or some other multi-tool.

These will handle most small adjustments.


seabob4 posted 05-17-2008 05:21 PM ET (US)     Profile for seabob4  Send Email to seabob4     
Mr. JimH is absolutely correct here in the usage of hex nuts and lock washers for proper battery cable installation. BRP specifies them, and Mercury also for Verado and OptiMax, as pointed out previously. But the point is, if you are using a "tool" to tighten a wing nut, why not put hex nuts on there, where you have to use a "tool" also? Besides, you should already have a 1/2" and 9/16" in your carry-on tool kit.
jimh posted 05-17-2008 08:04 PM ET (US)     Profile for jimh  Send Email to jimh     
Another important preventive maintenance procedure: apply distinct color code markings to all battery cables and terminals so that there is no possibility of reversing the polarity when making connections.

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