Ignition Coil/Resistance Wire question

[burtonrider11]

Hi guys, looking to swap my ignition coil this spring to one of the PerTronix Flamethrowers, most likely 45011. My engine serial number is 0K010675, 5.7l 2bbl Merc. TB4 ignition. I have identified the coil as original part number 392-7803A4 later referred to as 805570A2. In the research I did, it looks like this coil does NOT use an external resistor. However, it looks like I have a purple wire that goes to my existing coil. Is this a "resistance wire" and does it need to be replaced with a normal stranded wire to eliminate the resistance. I read that it looks like I can replace this wire with a new one coming from the choke. Not a big deal if I need to do so, just want to confirm prior to doing so. Any info would be greatly appreciated!

 

[Fishermark]

You already have electronic ignition with the TB4, so you should not have a resistance wire.

 

[burtonrider11]

Oh good deal! So then to replace the coil, it should be plug and play, provided I replace the coil with a similar spec'd coil? The Merc manual lists the primary resistance as .6-.84, secondary as 9,000-12,000 and inductance as 5.4-6.5.

Is is problem to vary from the the secondary resistances or inductance? I am assuming I need to match up the primary resistances closely.

 

[Fishermark]

That's more specific than I can answer. Why are you wanting to replace the coil? Are you having troubles, or simply wanting to "upgrade?" If you are having trouble, the answer is seldom as simple as "replace the coil." If you are looking for an upgrade thinking the Flamethrower will help - it will not.

 

[burtonrider11]

Well, I am changing out the old one for a couple of reasons. First, I've changed various ignition components already, cap, rotor, plugs and wires. This boat is new to us, but will be 19 this summer. So I am in the process of updating parts. My primary reason for wanting to swap coils is the hopefully help with starting when she's cold. I have played with the electric choke, but this boat is just extremely cold blooded. After she's warmed up, no issues starting. So it's most likely a spark or fuel issue. At this point, a $40 coil is cheaper than a new Mercarb or rebuild. And the PO told me the season prior he had a new carb installed.

I spoke to some people I trust with regard to engines and they told me it could possibly help to change the coil.

I don't want to start an argument with regard to the flamethrower coil being an upgrade, but I have read several comments stating that it IS an upgrade and it has helped starting and overall performance. It could be anecdotal or even placebo effect, I don't know. I will report my findings when I get it all done

However, at this point, I figure $40 to replace a nearly 20 year part that could be contributing to a problem isn't a terrible investment

 

[gm280]

Well, I am changing out the old one for a couple of reasons. First, I've changed various ignition components already, cap, rotor, plugs and wires. This boat is new to us, but will be 19 this summer. So I am in the process of updating parts. My primary reason for wanting to swap coils is the hopefully help with starting when she's cold. I have played with the electric choke, but this boat is just extremely cold blooded. After she's warmed up, no issues starting. So it's most likely a spark or fuel issue. At this point, a $40 coil is cheaper than a new Mercarb or rebuild. And the PO told me the season prior he had a new carb installed.

I spoke to some people I trust with regard to engines and they told me it could possibly help to change the coil.

I don't want to start an argument with regard to the flamethrower coil being an upgrade, but I have read several comments stating that it IS an upgrade and it has helped starting and overall performance. It could be anecdotal or even placebo effect, I don't know. I will report my findings when I get it all done

However, at this point, I figure $40 to replace a nearly 20 year part that could be contributing to a problem isn't a terrible investment

Well I will be surprised if it cranks any better myself. But that IS just my opinion.

 

[ihc1470]

I am with gm280 I doubt it makes much if any difference in the starting. Electricity is a strange duck, If a plug requires say 15k volts to fire than a coil will deliver 15k. If the same plug would require 35k to fire than the coil will deliver 35k if it can. If not than no spark. There is where the high voltage coils can make a difference. They are capable of delivering a high voltage. Does not mean that they will though. They only produce the amount needed to jump the gap. Before spending the money see how much gap the old coil will jump. They make adjustable spark testers or make your own. Heck you can even do it with an old plug just open the gap up to about 3 times normal and see if it will consistently jump that gap. Describe your starting issue cold in more detail as it might help in sending you in the correct direction for repairs.

 

[Bondo]

Well, I am changing out the old one for a couple of reasons. First, I've changed various ignition components already, cap, rotor, plugs and wires. This boat is new to us, but will be 19 this summer. So I am in the process of updating parts. My primary reason for wanting to swap coils is the hopefully help with starting when she's cold. I have played with the electric choke, but this boat is just extremely cold blooded. After she's warmed up, no issues starting. So it's most likely a spark or fuel issue. At this point, a $40 coil is cheaper than a new Mercarb or rebuild. And the PO told me the season prior he had a new carb installed.

Ayuh,.... Put the $40. bucks towards the carb kit, insteada wastin' it on a coil,......

You're not discribin' a coil issue,....

Coils are the most often changed part, because it's Easy, rather than any real reason to change it,.....
There's millions of perfectly good coils, tossed every year, for No good reason at all,....

 

[thumpar]

Make sure the carb that was put in is the correct carb setup for your engine.

 

[Alumarine]

I have to ask. Are you pumping then advancing the throttle using the "neutral" button when cold?

 

[burtonrider11]

Wow, lots of opinions here. I appreciate all the input. I will start a new thread shortly regarding cold starts!