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Author Topic:   Fried Ignition Switch
PCBrev posted 06-19-2006 07:38 AM ET (US)   Profile for PCBrev   Send Email to PCBrev  
Had my boat out for the [first] time on Friday and had an electrical problem.

I will try to describe but, if I leave out any vital information, please let me know,

Friday: my 2002 Johnson 60-HP four-stroke motor starts right up, runs strong for 30 miles (4 to 5 hours). Going along at 25-27-MPH, 4,600-RPM, I look down and tachometer gauge is dead but the motor is running great. I stop the motor and smell burning coming from under center console.

Under console I find that there are 6 wires coming from the key switch and one of them (purple) has melted through [its insulation]. Turn key, motor turns over, doesn't start, dead.

Get towed in and find a guy with a new wiring harness, change fuse (on top of motor) and she fires right up. Wiggled the wires under key switch, dies again.

Saturday: New ignition. She fires up runs for 15 minutes. no problem.

Sunday: she ran strong all day until I was banging along around 32 MPH in some chop the motor cut out again. I stopped, checked fuse (fine) pushed on all connections and starts right up again.

I'm bringing her to my Johnson guy and was wondering if anyone here had any thoughts?

This is my first four-stroke for a recreational engine and I'm lost as to all the electronics.

Any advice or experience would be greatly appreciated. I'm sure I left something out but I'll check back often and add any relevant information.

jimh posted 06-19-2006 08:51 AM ET (US)     Profile for jimh  Send Email to jimh     
Usually the violet conductor in the wiring harness carries the switched 12-volts from the battery when the ignition switch is in the RUN or START positions. If the wire insulation melted that is a sure sign of excessive current. The motor must have voltage on this lead to run.

The battery supply to the ignition switch should be fused under the engine cowling. It sounds like in your case the current being drawn was not high enough to open the fuse, but too high for the wiring to handle.

Check the fuse to be certain it is the proper rating.

Check all the connections in the violet-lead's circuit. It sounds like something is loose. If the engine stopped it is a good indication that it lost voltage on the violet lead coming back to it from the ignition switch.

PCBrev posted 06-19-2006 09:52 AM ET (US)     Profile for PCBrev  Send Email to PCBrev     
S
PCBrev posted 06-19-2006 10:02 AM ET (US)     Profile for PCBrev  Send Email to PCBrev     
Sounds right, it did blow the fuse under the cowling the 1st time, when it fried the wire.

Because I still haven't figured out why it fried the wire/fuse to begin with I'm still concerned.

Could a loose connection have caused a short that caused the melting wire/blown fuse?

There are so many wires compared to my 40 hp 2s I'm used to. Can you give an educated guess where to start?

Because the tach went dead 1st (motor still running great), I didn't hook that back up for my test yesterday. Could the short originate there or is it just a coinsidence or a side effect of the power supply problem?

As an aside, when I connected the lights to the battery, the cables were already run (not colored pos/neg) and I just guessed and tested, they worked. Could i have crossed a wire that would cause this?

I hate electrical/engine gremlins, no piece if mind.

jimh posted 06-19-2006 01:22 PM ET (US)     Profile for jimh  Send Email to jimh     
Incandescent electric lightbulbs do not have a polarity. You can connect them to a voltage source without regard for polarity.

When connecting a battery to the boat main power distribution it is crucial to observe polarity. Connection of the battery to the boat wiring with the polarity reversed will cause immediate and expensive damage to the rectifier in your alternator circuitry.

PCBrev posted 06-19-2006 01:33 PM ET (US)     Profile for PCBrev  Send Email to PCBrev     
Cool- I had the polarity correct for main power.

I'm going to go over all connections before next trip.

I really want to find the cause and not just have it vanish.

jimh posted 06-20-2006 12:44 AM ET (US)     Profile for jimh  Send Email to jimh     
You should carefully identify and mark all the cables in your primary electrical system which connect to the battery with colored electrical tape. I recommend SCOTCH 35 Vinyl Electrical Tape. It is available in at least eight colors. Use RED for the positive terminal leads, and YELLOW for the negative terminal leads. Also mark the terminals on the BATTERY itself. If you spend $5 on this now you will avoid a disaster in the future.

If your boat has all the cables which connect to the battery already color coded and also has batteries which have the terminals color coded, you are free to ignore this advice, however, you probably are not in that situation and should take heed of this recommendation.

Usually when I offer this advice someone pipes up to say how silly it is, but those are guys who have not yet hooked up their battery with the polarity reversed. After they do, they'll come over to my side.

PCBrev posted 06-20-2006 07:01 AM ET (US)     Profile for PCBrev  Send Email to PCBrev     
LOL, will do. A little preventative maintinance.
PCBrev posted 06-23-2006 09:26 PM ET (US)     Profile for PCBrev  Send Email to PCBrev     
Well I put a brand new wiring harness, new ignition, coded all the wires and took it out today. Foggy around Portsmouth today so I wasn't trying to set speed records but banged around fairly hard with no engine cut-outs/ignition issues.

Still not convinced I've solved the problem but if it happens again I'll have eliminated some possible sources.

Ordered a Standard Horizon PS1000 Phantom VHF w/White RAM+ from
a tip here on CW (thank's Tom $99.99) so I'll color code the wires and install this week.

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