what is a ballast resister circuit and wheres it located

[lovesboats]

I am totally boat illiterate. I know about cars. but boats nothing at all.frosty told me my boat needs a ballast resister circuit. What is that? what does it look like? and where is it located? anyone have a picture of one? If so send it to me at lovesboats@hotmail.com ..Also just for reference. what my boat is doing is when I turn my ignition key over the boat is like running fine but backfiring sometimes. as soon as I let go of the key it stalls. so basically my boat stays running if I hold the ignition key over on start. I replced the coil. the plugs. cleaned the points and all the terminals. it gets fuel and spark. I really need to get this running so I can sell it. I have no room for the boat and need the money bad. The boats nice. by the way it is a 1987 19.5 foot sea ray "seville" cabin cuddy . it has the big 4... 3.0 liter mercruiser. with alpha one outdrive. nothing wrong with boat boat except for that problem. boat ran perfect all summer . with no problems at all.

[lewisboats]

Sounds like it slipped the timing, maybe stripped the distributor gear.

Steve

[longliner45]

do you have a mopar or chrysler product ,motor?

[TerryKing]

The symptom you have (Starts, but stalls as soon as you let off the starter) certainly sounds like a bad ballast resistor (assuming you have one!)..

Pre-Electronic Ignition systems use a contact points-condenser combination to switch current into the coil primary winding.

To aid starting, most systems have a coil that is actually rated for 6 Volts, and connect a resistor in series with the coil primary when running. (This also helps high-speed spark). BUT they often make a connection from the starter motor relay to the coil so that it gets a direct 12 volt 'boost' for low-speed starting.

Use a voltmeter to debug this. Check the two low-voltage connections on the coil with the engine stopped. Put one end of the meter to ground.

With ignition on, check the connection from distributor to coil. With the points Open there should be 12 volts, and Zero with the points closed.

With ignition on, check the other coil connection. It should have 12 volts when the points are open and about 6 volts or so when the points are Closed.

If you have no voltage on the coil primary with ignition on, but it comes up to 12 volts with the starter running, the 'ballast resistor' is probably open (or possibly there is some wiring problem or a bad ignition switch)..

The 'Ballast Resistor' is connected from the ignition switch output to the coil. It can be either a small resistor (often a rectangular white ceramic thingie about 2 inches long) OR in some cases the WIRE that goes to the coil has an intentional resistance to it. The resistance VALUE is often between 1 ohm and 1/2 ohm.

Just start by looking for 6 to 12 volts on the coil terminals with ignition on and engine stopped. No voltage there makes the resistor the suspect...

Let us know what you find!

[lovesboats]

can I hook a wire directly to the output on igntion switch directly to the coil to if that fixes the problem? to find out if it is the ballast resister is bad? because if it starts by me hooking another wire directly from ignition to coil. and if it starts that should let me know if it is the ballast resister or is that a bad idea? also which wire on the back of the ignition switch is the output? or which wire?

[TerryKing]

Originally Posted by lovesboats

can I hook a wire directly to the output on igntion switch directly to the coil to if that fixes the problem? to find out if it is the ballast resister is bad? because if it starts by me hooking another wire directly from ignition to coil. and if it starts that should let me know if it is the ballast resister or is that a bad idea? also which wire on the back of the ignition switch is the output? or which wire?

MMM.. The problem here is Electricity is INVISIBLE! Can you just get a small 12V bulb connected to a couple wires? (Parts stores have cheap "low voltage testers" that look like a fountain pen with a ground wire)..

IF you're real sure which coil connection is NOT going to the distributor points, you can connect it very temporarily to 12 volts. If the engine runs, shut it down and find the real problem.

But you really should use some 'Voltage Visibility' thing and trace this out...

[lovesboats]

Ok so if I hook a single wire from the key ignition output (point A) (where the ballast resister circuit wire hooks to at ignition key) to positive on coil (point B)(where the ballast resister circuit hooks to on coil) just for a second and the boat starts. then the resister wire is the one that needs tobe replaced correct? just to see if it is the ballast resister. Also as soon as I unhook it(the wire from coil) the engine will shut off correct??? just need to know this. I mean it should work. and how long can I leave it running before it causes any damage??

[Frosty]

Youve got two threads running here.

Put a wire from the battery or any posative to the coil ( not to the wire that goes to the points -the other one). If the engine runs ,it is ign sw , feed wire -or ballast resistor.

Then try it to the in side of the ballast resistor,--if it runs its the feed wire or ign sw. Dont dismis the Ign sw its common for them to fail.

Basically for a reall quick Diagnosis,-- put the feed wire on the switch to crank feed on the sw. If it runs its the switch.

Try googling-Im sure there must be loads on this stuff with wiring diags.

[PAR]

The "big 4... 3.0 liter mercruiser. with alpha one outdrive" as you put it is a GM 181 cubic inch iron block, previously available in the late sixties Chevy Nova (only two years I think). It's a very common engine.

When you throw the key to the start position, the ballast resistor is bypassed. This is because of the 25% or so voltage drop that occurs from the demands of the starter when cranking. On a stone cold engine you'll have about one ohm of resistance across the resistor.

First off you need to identify the ignition system on your boat. It's likely a Thunderbolt IV, but who knows what is hanging off the front of that Alpha, so run the numbers or look for the ID plate. You probably are in need of a repair manual at the very least. These types of problems are easy for a mechanic to sort out, they've seen it dozens of times before and know just where to look and with what tool. Personally, I think you don't have a ballast resistor on that ignition system, nor points or condenser. A quick look under the cap will tell if this is correct. I think you have a bad connection on the "IGN 1" circuit, either inside the ignition switch itself (likely) or in route to the engine bay.

I could ID the real problem with your Sea Ray in just a few minutes, if it was here in the yard. You have three options as I see it; get a repair manual and sort through the ignition section tests yourself (meaning you have a reasonable grasp of the concepts and principles) or you could bite the bullet and have a pro fix it and lastly you might get lucky, not burn up additional parts from touching wire to things you hope will not be harmed and some how muddle through.

I'm not trying to be coy with you Lovesboats, but this is a quick and easy fix. Not knowing what we're looking at (engine year and type, ignition type, etc.) makes it a bit of a crap shoot with a diagnoses. For what it's worth, unless you do a great deal of idling and no wake cruising, your ballast resistor (if you engine even has one) isn't likely bad (they get quite hot at idle and at very low RPM's). I've seen original equipment resistors, still in service 40 years later. Have a mechanic look her over.

(Duplicate reply from other thread)