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help and advice mercury outboard

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aussie boatie

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1988 mercury 90 hp in line 6 cyclinder after reading some outher post here regarding the engine not turning off from the key
iam having the same problem only thing different it will turn off its cold but not when its hot the engine will die down but keep running
ok how do I tell witch switch box is bad the engine starts ok and runs ok any advice or help is appericated I have put in a kill shut off switch at the moment aussie boatie
 
One of the posts on EACH switch box is grounded to kill the motor. (Usually a black/ yellow tracer wire, but sometimes an orange one.) Remove the kill wires from the switch boxes and see which goes to ground (key off). The one that doesn't has a break somewhere.


G-day and good luck.

Jeff
 
good morning thank you for your reply I had all ready did a contuinity test ith a mulimetter and checked all the earth wireing right back to the igniton switch and it seam to be all good the black with yellow trace runs one wire from switch to the engine then they have joined it to split three ways one going to kill swich on the motor then one to top switch box the outher to bottom switch box that lot all have counitanity as all way any advice or help is appericated
aussie boatie
 
If you short the black yellow wire terminal on the switchboxes to ground and the engine stays running the switchbox or boxes are bad and need replaced.
 
at the moment the kill switch I have put on is earthed to the motor th black wire to the kill swich and the red on on the kll switch is conneted to thethe blue coloured conection on the bottom switch box coming from the stator and when I swtch the key off it still runs then I turn the kill swith t h on postio it will kill the engine ............
 
http://www.maxrules.com/oldmercs/Wiring/1966ona/37.jpg
I believe this is the diagram for your motor both of the switchboxes black/yellow wire should be wired together when you short that to ground the engine should stop. Sounds like you have some wiring issues you need to address never apply battery pos to the kill wires or you will need new switchboxes. The ignition system is totally independent of the charging system. You cannot use a car ignition switch it must be a outboard switch.
 
again thank you yes i do have that digram in a workshop manual i think i have writen down the kil set up badly i have not got any batt power going in t the switch box the red wire is runing straiht to the kill switch and the black wire is earthed to the motor the kill switch is seperat set up its justatwo wre on a toggle switch and iam still useing the mercuy igniton switch
 
iam worending if i move the red wire from the stator wire on the the black and yellow trace wire and see if it will shut off from the toggle set up on both of the switch boxes and see if it will shut off that way or one switch box at a time and try that to see witch switch box is not working proptly would that work
 
''only thing different it will turn off its cold but not when its hot the engine will die down but keep running ''
you didn't start out with a wiring or kill switch problem...put all the wiring back to original...use a timing light on the engine when it fails to stop and see if it is still firing...if it is not then pull and replace the plugs and decarbon engine...
 
good evening ok i can check with a timming light do i check the spark on all the plugs the plugs are all new only been out a couple of time would say only acouple of hours old but will take out and check for carbone build up
 
ok here where i am up to now I did put the timing light on all the plugs wires and find only 1 and five stop fireing after the key is turned of and the engine will only stop if I earth the blue stator wire on the bottom switchbox and it will not stop even if i earth out both black and yellow trace wires on the switesboxes he thisgive you more information to work with thank you
 
Sounds like the next step just make sure everything is correct before you connect the battery. All it takes is a split second of battery pos to the black/yellow kill wires to cook the switchboxes. Leave the kill wires off the switchboxes and double check the ignition switch is working correct and your not getting power to the kill wires switching through the positions. The switchboxes are not terribly expensive but you need to try and determine why they went bad if possible. A DVA adaptor will help you determine if everything is looking and smelling good before you put it into service. A volt meter is a good upgrade if you dont have one you can keep a eye on charging voltages.
 
thank again I have a digital multi meter and I did a voltage check earlier after reading the link you posted I had the egine running and put the red wire of the multi mete on the black and yellow wire and the blackwire of the multi to earth no power reading have to worender why the problem with the sitchbox as the egine starts ok since I put in a 100amp battery as before that t was very hard to start but there was a problem last time out the engine just stoped while running only way I gotback to the ramp was to keep pumping fuel but I changed the fuel line from the tank seamed fix that problem as then the engine was still stoping with the key the problem seam to have happened since I put the new bigger battery
 
fastjeff said:
Wheeew! Bet your wallet got a bunch lighter!

Jeff
Click to expand...

hi to the forum well the two new switches boxes have arrived and fitted so far its all good news it even started much easier and its seam to be idleing much better and I let it idel for about ten minutes and so far its switching off from the key the price was not to bad did an ebay search and go some brand new one quite cheep delivered all the way from the states to Australia thank t the forum
 
Good to hear, do you have a volt meter on the dash? Its good to keep an eye on the voltage at high rpms, if over 15 volts you want to address the issue. Use a older type car battery lead acid type is the safest. Another thing you can do is add some high amp draw appliances to use the extra power produced at higher rpms. Make sure it is charging properly so you dont cook the new switchboxes. One of those 12 volt refrigerated ice chests are a fine addition to any boat. Keep the fishes and the beer cold:)
 
thanks will check the voltage with the multimeter at the moment iam useing a car battery and running a navman fish finder radio 2 marine two radio and a navigator will look into a small 12 volt fridge thank for the advice
 
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