Electrical systems on outboard boat motors

17 Dec 2014 | Author: | Comments Off on Electrical systems on outboard boat motors
Mercury Mariner

The electrical system of a boat can range from being fairly simple all the way to an electricians nightmare depending on the type of boat. This can be very discouraging to many people when troubleshooting an electrical system. One thing to remember though, is that most manufacturers pretty much stick to a standard when it comes to electrical system design.

If you have purchased a used boat from someone that thought they were an electrical wiz, only to totally cluster any way of tracing a problem due to using whatever color wire they could scrounge up to replace or add an accessory, I really have no way to help you, but definitely feel for you because I have run across that problem so many times I felt like locking the doors and tacking a for sale sign on the front door. In this section we will look at some basic wiring diagrams and list some of the color coded standards that are common on almost every boat made. We will look at some of the electrical components on inboard/outboard motors and also some of the other boat accessories, and how to troubleshoot problems with them.

Motor Components

Other than the ignition components which are covered in the ignition components section, there are a few electrical items on an outboard motor that can cause problems.

Lets first look at the marine battery.

Why bother using a more expensive marine type battery when an automotive type will work to start my motor? Wrong!

Only the rich can afford cheap automotive batteries for use in a boat.

To a degree the previous question is true, but there are some major differences in automotive batteries and marine batteries. Actually, a marine battery would probably make a better application than an auto type battery in your car or truck. Marine batteries are designed with more cranking power, more reserve power, and a deep cycle duty that will provide you with at least 150 deep discharge cycles if properly maintained.

Outboard motors DO NOT always maintain a full charge in your battery. The amp output of an outboard stator usually does not output enough juice to keep the battery at full capacity like an inboard/outboard does. Routinely charge your battery between outings to make sure your battery stays in good condition.

People kill batteries faster than old age due to improper charging and maintenance! Recharge battery as soon as possible after discharge. Never allow a battery to sit for long periods in a run down state.

Use an automatic charger only, with 10 to 20 amp output to charge marine batteries, and never overcharge.

The only other thing to say about a battery is keeping the cable connections tight and free of corrosion. If you disconnect your battery cables, make sure to NEVER cross cables to the wrong post. Connecting your battery backwards can instantly pop the rectifier in the charging system.

Starter and Starter Solenoid

Mercury Mariner

A starter can be one of the most used and abused components on the marine engine. Besides being under constant attack of moisture and corrosion, a starter can undergo much strain, especially if something is keeping the motor from starting. For instance, if the motor has a no fire condition, and a person continually cranks and cranks with the starter in hopes that something in the cranking will fix the no fire problem, the starter is bound to practically burn itself up from the abuse.

If your motor does not fire up within a few seconds of cranking it with the starter, stop and find out whats wrong. A motor in proper adjustment and good condition internally should never take but just a few revolutions to start and run. Starter problems can range from just plain being worn out, to corroded inside, to being burned up inside.

So you go to crank the motor and all you get is a click sound out of the starter. What could be wrong? First make sure your battery is in good condition, that there is no corrosion on terminals, and that cables are TIGHT!

A loose cable connection can cause you unwarranted expense on replacement starters and batteries that were never bad in the first place. If you ever get water in the starter(submersed), replace it right then and there. It will probably still work ok for a while, but sooner or later its history and you’ll be stuck on the lake, guaranteed! The easiest way to tell if the starter or solenoid is bad is simply to test system with a voltmeter.

If you only get a click, attach negative lead of voltmeter to ground, and the positive lead to the yellow/red stripe wire on the solenoid. Try to crank motor. Does the voltmeter show a full 12 volts at the yellow/red stripe wire? If so, replace solenoid and starter as a pair.

If not, the problem is not the starter. Trace Yellow/red stripe wire to key switch to make sure there is 12 volts to the switch connections.

Oil Injection

On outboards that contain oil injection, there are a few electrical components that all work together to perform the mixing and monitoring of oil/fuel injection operation. These components can vary greatly in the way the operate from one motor brand to the other. Most though, have 3 common elements.

An oil tank is usually located inside the boat and can contain anywhere from 1 /12 gallons to 3 gallons of oil, depending on the size of the outboard. The oil tank also contains a sensor which monitors the oil level of the tank. If the oil level reaches a low condition, the electronics of the oil injection system will send a signal to the warning horn, which in turn, notifies you of the condition. The warning horn usually sounds off with intermitant beeps, and normally you have approx.

45 minutes running time of oil in reserve. DO NOT ignore this beep, as running out of oil means instant death of the powerhead.

The second component of the oil injection system is the pump. Some models contain electronic control of oil mixture, and some models use a mechanical application. The mechanical application is much more dependable, although the electronic type have improved in dependability over the last few years.

To troubleshoot an electronic type pump, please refer to your repair manual.

Lastly, the oil injection module is the brain of the system. Sensors tell the module what is going on, and the module acts accordingly to the situation. Todays oil injection systems will alert you when something is wrong, and some even shut down motor operation to protect from severe damage.

Again, please refer to your repair manual to troubleshoot your specific application.

Mercury Mariner
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