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  40-HP Mercury Makes Strange Noises When Ignition Key Moved to START; Does Not Crank Over

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Author Topic:   40-HP Mercury Makes Strange Noises When Ignition Key Moved to START; Does Not Crank Over
Langella7 posted 05-31-2011 09:52 PM ET (US)   Profile for Langella7   Send Email to Langella7  
When I store my boat after a trip I disconnect the positive leads to the battery, in case it drains for some reason (haven't gotten a battery switch yet ). Before I go out I hook them back up and raise the [2005 Mercury 40-HP outboard] engine. At launch I lower engine.

When I go to start engine you hear a pop like a fuse blowing and nothing happens, and nothing works. If I disconnect the positive leads again and reconnect them right away [the engine] starts up and starts up without any problems.

This has happened at least five of the 10 times I've had [the Mercury outboard engine]. Its a 2005 130 SPORT with Mercury 40-HP, not much electrical to it. I have three leads, two for the boat and one for the fish finder.


Anyone have any ideas?

jharrell posted 05-31-2011 10:52 PM ET (US)     Profile for jharrell    
Sounds like an auto-resetting breaker, they act like that.

Not sure where you would have one in your system, my jack plate has one and looks similar to these: http://www.wiringproducts.com/contents/en-us/d60.html

Maybe the Mercury has one for the power lift that affects the ignition or for some other purpose.

pcrussell50 posted 06-01-2011 12:37 PM ET (US)     Profile for pcrussell50  Send Email to pcrussell50     
Could also be a bad connection to the battery, causing weak current to the starter. The pop you hear could be the solenoid clicking or starter bendix having just enough juice to sling up the pinion gear, but not enough to turn the flywheel. If the motor's ring terminals aren't clean and shiny, it can cause this. Then, when you re-rack them, it makes a better connection, and works fine. I used to see it all the time when I disconnected my battery often, (not for winter, but to use the battery to start on old car, whose battery had gone bad, and I was too lazy to buy a new one.) Now, I clean the ring terminals till they shine, then coat them in some die-electric tuneup grease and clamp them down tightly to keep out air and other other oxidizing agents, and keep it that way. Always works right... but I always bring a wrench in case it happens out on the water.

-Peter

djahncke posted 06-01-2011 03:42 PM ET (US)     Profile for djahncke  Send Email to djahncke     
You don't want to cover it with dielectric grease before you connect. That stuff is non-conductive by definition (hence the term dielectric). Dielectric grease is used after you make the connection to help seal out moisture.

-Don

jimh posted 06-01-2011 07:56 PM ET (US)     Profile for jimh  Send Email to jimh     
Don--Good luck trying to convince boaters not to smear insulating grease all over electrical connections before connecting them. That bad advice has been repeated so many times that it has become its own legend and the people who repeat it are now legendary.

I can't imagine what the noise you are hearing from the motor might be. I suggest you remove the cowling of the motor. Have an assistant perform the process that produces the noise while you listen closely to the engine to see if you can identify the source of the noise.

In any electrical circuit where the power is supplied by a battery, if there are problem in the circuit's operation, the first component to isolate and verify as good is the battery.

pcrussell50 posted 06-05-2011 05:09 PM ET (US)     Profile for pcrussell50  Send Email to pcrussell50     
quote:
You don't want to cover it with dielectric grease before you connect. That stuff is non-conductive by definition (hence the term dielectric). Dielectric grease is used after you make the connection to help seal out moisture.

True, as far as it goes. But dielectric grease is a lot more conductive than the oxide layer that is the probable cause of your clicking. Of course, good practice is to tighten down your (clean) ring terminals with a wrench. Usually, this is sufficient to prevent salt-air-oxygen from getting to the ring terminals. If you are a frequent r'n'r'er of your battery, as I am, I use wing nuts that don't get nearly as tight as a properly wrenched, nut. Grease keeps the oxide layer from forming on my ring terminals, yet is so thin, it passes plenty of current to crank my boat motor.

On my fresh water boats, I also remove the batteries frequently, but I don't use dielectric grease. The dry desert air and lack of salt, where I keep them does not warrant it's use.,

-Peter

jimh posted 06-07-2011 08:43 AM ET (US)     Profile for jimh  Send Email to jimh     
If you have an iPhone or other smart hand-held mobile device, use the audio recorder in the device to record the strange noise. Post the audio file somewhere where we can listen to it. It is difficult to make a diagnosis from a narrative description of a sound. In the modern era of electronics you can easily record the sound and allow us to hear it, too.
Langella7 posted 06-21-2011 11:16 PM ET (US)     Profile for Langella7  Send Email to Langella7     
I have taken the boat out a few more times. It is still [making a noise then losing all battery power], but now sometimes it starts for the first time of the day, then will do [make the noise and lose battery power] later on in the day.

To highlight, sometimes when tyring to start the engine it will make a single poping noise like a fuse is blowing or a breaker is tripping. After this pop, nothing works, and there is no power trim. When I disconnect all the positive leads to the battery and reconnect them the engine works, starts, electronics work, and usually [all electrical devices] work for the remainder of the day.

I can't see how [the cause is] a weak connection since nothing works after this pop. I searched the boat and can't find any breakers or fuses. What can this possibly be? I opened the engine and found a fuse box, but I really don't want to go screwing around with this.

Any ideas [what is causing the pop and the loss of electrical power]?

jimh posted 06-22-2011 07:53 AM ET (US)     Profile for jimh  Send Email to jimh     
You need to locate the point in the circuit where there is a loss of continuity from the battery. The next time the electrical outage occurs, investigate the circuit using a portable voltmeter. Connect the negative lead of the voltmeter to the negative terminal of the battery. Wait for the electrical outage to occur. Begin checking for voltage by connecting the positive lead of the voltmeter to various points in the circuit. Connect the positive lead to:

--the positive terminal of the battery
--the terminal lug of the battery cable at the positive terminal of the battery
--the conductors of the battery cable at the positive terminal of the battery

Then proceed along the battery positive distribution circuit. In a separate article I list about 50 places to check. See:

Electric Starting Circuits
http://continuouswave.com/whaler/reference/electricStart.html

Check the circuit at all those points until you identify the point where there is a discontinuity.

jimh posted 06-22-2011 07:55 AM ET (US)     Profile for jimh  Send Email to jimh     
My rule for diagnosis of problems like this:

In any electrical circuit powered by a battery, the first component to check for being the source of trouble is the battery.

Verify that the battery itself is not the source of these problems. Temporarily substitute a known-good battery.

jimh posted 06-22-2011 09:06 AM ET (US)     Profile for jimh  Send Email to jimh     
The "pop" noise could be from a small explosion of hydrogen gas around the battery. The source of ignition could be a spark from a loose battery terminal connection or perhaps a loose internal connection in the battery.

Temporarily replace the battery with a battery known to be good, and see if the problem with the "pop" and loss of electrical power remains.

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