direct wire testing for ballast resister circuit

[lovesboats]

Can I hook up 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 to see if the boat starts. AND IF THE BOAT STARTS then the resister wire is the one that needs to be 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. Also how long can I leave it running before it causes any damage?? Id like to run it for a few minutes if possible.

[marshmat]

I'm not quite certain how your rig is wired up so I can't say absolutely for sure whether what you propose is an OK test.
The "ohms" function on your multimeter is probably the easiest and most accurate way to check if the ballast resistor is damaged.

[Frosty]

You can connect that way to test it and no you are doing no harm for a while unless you have disconnected the ballast resistor itself in which case you would be running the 10 volt coil on 12 volts, still Ok for a while max 1/2 hour.

If you put the wire from the ballast to a posative supply( any where) and the engines runs normally,-- it is your Ign switch.

[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)