1987 Mercruiser 5.7 260 Ski Ignition

DHillery

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Sep 21, 2004
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Hello All,<br /><br />I own a '87 Malibu Sunsetter with a Mercruiser 260 Ski inboard. I'm replacing the old breaker points distributor with a Mallory magnetic breakerless distributor. The instructions for the new Mallory dictate that a ballast resistor or resistance wire be installed between the ignition switch and the coil. How do I find out if either of these is already installed? I have checked the wiring schematic in the operation and maintenance manual, and if one is there it's not obvious.
 

DHPMARINE

Captain
Joined
Dec 16, 2003
Messages
3,688
Re: 1987 Mercruiser 5.7 260 Ski Ignition

You probably don't have a ballast resistor.Older Mercs did.Check the wire that feeds the distributor.With the key on,it should have LESS than 12Volts.That means it is a resistor wire.<br />DHP
 

DHillery

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Joined
Sep 21, 2004
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3
Re: 1987 Mercruiser 5.7 260 Ski Ignition

DHP - Thanks for the quick response. There are two wires on the positive side of the coil, one has no voltage with the ignition on and the engine not running, the other has 12.5 volts with the ignition on and the engine not running.
 

elpaso

Petty Officer 1st Class
Joined
Jun 27, 2003
Messages
264
Re: 1987 Mercruiser 5.7 260 Ski Ignition

Check - " Search at top of page - ignition resistor - " there must be 20 answers to your resistor question. In last year I have posted 8-9 answers to this problem.<br /><br />If you can not find any help - I will post diagram and wiring help.
 

rattana

Chief Petty Officer
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Jun 12, 2003
Messages
413
Re: 1987 Mercruiser 5.7 260 Ski Ignition

One will have full voltage when the key is in the start position. The other wire would have a reduced voltage in the run position if a resistive wire or ballast resistor is inline with it. If it is full battery voltage in the run position either there is no resistive wire or ballast, or it has been bypassed.
 

DHillery

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Sep 21, 2004
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Re: 1987 Mercruiser 5.7 260 Ski Ignition

Thanks for the tips, all quite helpful. Here's where I'm at. I'm the original owner of the boat, so I know the wiring is as it was when it floated out of the factory. The new breakerless distributor is installed. I'm trying to avoid cranking the engine at this point to keep it in a known state as far as the timing goes until I'm sure about the wiring. I'm using the stock coil with a "use external resistor" label. There are two wires on the + side of the coil; purple/yellow going to starter solenoid, and either faded purple or pink, (it's hard to tell) the wiring schematic indicates that it should be purple. I now understand the role of the wire coming from the starter solenoid is to provide a full 12v while the starter is cranking. The other wire is energized with the key in the run position but it shows a consistent 12.4v whether it's attached to the coil or loose. I'm guessing that because of the lack of actual contact points in the new distributor, I'm not seeing a drop in voltage since there is no current in the circuit (other than what the meter is drawing), hence no resistance. With this in mind a put a small test light in the circuit and show a drop in voltage to about 11.8v. Shorting it directly to ground brings the voltage down to .5v and the wire gets noticeably warm. I'm assuming that these would be characteristics of a resistance wire. Am I on the right track here? Is there any advantage to bypassing the resistance wire and installing a ballast resistor in its place?<br /><br />elpaso - Please pardon my newbieness, but as a matter of fact I did do a search before posting, it was just too specific to my application to turn up anything useful. Maybe I'm taking your post the wrong way, but if you are going to get your undies in a bunch about answering a question more than once, maybe you should take a break. A simple direction to a previous post is all that is required.
 

elpaso

Petty Officer 1st Class
Joined
Jun 27, 2003
Messages
264
Re: 1987 Mercruiser 5.7 260 Ski Ignition

http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=24;t=007471#000003 <br />First one on list.<br /><br />You did not look very hard - try search <br />ignition resistor - <br /><br />Sometimes you have to "help" yourself - no one wants<br />to spend 1/2 hour typing out something that has <br />been posted 50 times in 2 years. And posting wiring diagrams for the 5 time.<br /><br />I tried to help you - and you attack - <br /><br />You say you have a manual - the wiring diagram is simple.<br /><br />Resistor wire is from choke to coil, on a 87.<br />Who knows what has been changed in 17 years.
 

Hog Wild

Seaman Apprentice
Joined
Aug 29, 2004
Messages
40
Re: 1987 Mercruiser 5.7 260 Ski Ignition

This statement DHillery made is incorrect: "I'm guessing that because of the lack of actual contact points in the new distributor"<br />The resistance will be the same with the new system. All the resistor is for is to limit current flow to the coil.<br />Why are you even worried about this if you are using the stock coil? Same coil, same wire faded wire connection you had connected to it before? The resistance wire will not like wear out. If it fails the boat will not run because the coil will not get power. I'm thinking you are getting fooled with your voltage readings and the resistor wire is working fine. But if you are scared of this, it is ok to put a ballast resistor in place instead. Shorting the wire to ground will cause it to get hot.
 
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