Mercruiser 3.0 L (Ignition)

[Kelsey]

Battery is being drained each week when I go to use it. Traced problem back to two purple wires running off of the ignition switch. Can someone tell me where these wires go to or what they control. Engine will not start with these two wires disconnected but will turn over. No power is being drained from battery once I have disconnected these 2 wire. Any Ideas out there?<br /><br />Thanks to all <br /><br />Cheers, Chiboka

 

[Trent]

Re: Mercruiser 3.0 L (Ignition)

What year model?

 

[Boatin Bob]

Re: Mercruiser 3.0 L (Ignition)

The purple wire is your ignition wire and goes to the coil, plus other places. Try using a meter and see if there is power at it with the key off. Then remove the wires and see if there is power on the terminal with the key off, if there is then it sounds like the switch maybe shorted.

 

[Bondo]

Re: Mercruiser 3.0 L (Ignition)

Purple wires on a Mercruiser are the Ignition Circuit.............

 

[Kelsey]

Re: Mercruiser 3.0 L (Ignition)

The make of the boat is a 1986 16 1/2 ft thundercraft 140 horse 4 cylinder.<br /><br />Chiboka

 

[Kelsey]

Re: Mercruiser 3.0 L (Ignition)

Tested ignition switch wiring. Battery wire on ignition switch has power, start line has no power and "I" (purple wires) terminal has no power when key is off. When key on power goes on on those two lines.<br /><br />Chiboka

 

[cobra 3.0]

Re: Mercruiser 3.0 L (Ignition)

Your battery is dead after a week of sitting? Could be just an old battery needing replacing. Does it charge up full with a charger?

 

[Kelsey]

Re: Mercruiser 3.0 L (Ignition)

New deep cycle battery. <br /><br />Chiboka

 

[Boatin Bob]

Re: Mercruiser 3.0 L (Ignition)

Sounds like the switch is working as designed except the S (start) terminal should have NO power when switch is on, only when you turn it to start. Curious how you traced the problem to those 2 purple wires and why you think that is your problem. Do you have a battery switch on the boat? If wired properly this should kill all power to everything (of course you need to wire bilge pump, stereo memory, detectors separately).

 

[Kelsey]

Re: Mercruiser 3.0 L (Ignition)

I will do some more testing this weekend to see if I can identify the problem. Thanks to everyone who was able to give me some ideas.<br /><br />Chiboka

 

[Kelsey]

Re: Mercruiser 3.0 L (Ignition)

Here is what I came up with. Problem still not fixed. Traced wires back from battery to find out where the power draw is coming from. Reversed wires at regulator on alternator & power drain stopped at battery. Now problem is that the motor will not turn off after it is started. Alternator is puting out 14.70 volts at battery terminals. I believe I am going in the right direction but very frustrated. Dam horses flys keep biting and bothing me. Thanks for any help.<br /><br />Chiboka

 

[Kelsey]

Re: Mercruiser 3.0 L (Ignition)

Any thoughts guys<br /><br />Cheers, Chiboka

 

[Boatin Bob]

Re: Mercruiser 3.0 L (Ignition)

If it won't turn off, sounds like you've managed to put an unswitched 12volts on the coil, wouldn't leave it like that, will pull the battery down for sure or burn out the coil. Was anything done to the engine prior to your problem?

 

[Kelsey]

Re: Mercruiser 3.0 L (Ignition)

The only thing that was done to the boat was change the alternator & battery.<br /><br />Chiboka

 

[hoot]

Re: Mercruiser 3.0 L (Ignition)

my boat is older. my start diagram shows this in general. one wire to switch (a)is fed from alternator/battery thru the ammeter to the switch. this supplies power to the switch to crank and run. one wire (b) goes back to the slave solenoid to activate it for starting. the third wire (c) goes thru the oil pressure gage, to the water temp gage, and to the coil thru the resistance wire. at start, a and b wire terminals are connected. this activates the slave solenoid which activates the starter solenoid which supplies currrent to the starter motor and ~12 volts to the coil + side. after the motor starts, terminals a and c are connected. this gives a reduced voltage to the + side of the coil. when shutting down, a and c disconnect and current to the coil is lost. if motor is not shutting down, you have some wires crossed somewhere.