Mercury thunderbolt IV ignition advance module question
 

I just put a new 502 in a 1989 Switzer SS240. I'm currently using the Mercury Thunderbolt IV distributer that came with the boat. My ignition module is a V6-14. After setting the initial advance at 16 degrees, I checked the total advance up to 4500rpm. The advance did not change at all. Is this the typical sympton of a bad module, meaning that the engine runs fine, but dosen't advance the timing? Could I have done something wrong with the wiring such that the distributor functions, but won't advance?

Anybody got a used/cheap V6-14 or V8-20 ignition module, or should I upgrade to a new distributor?

Maybe you could borrow any Merc module for a test, then make your decision. Why would the wiring be off with a plug connector in the wiring harness? Make sure it has a good ground.

What is your idle speed? The v6 is looking for 3 pulses per revolution, when on a v8 it is getting 4, this means that if you are idling at 1000 the module thinks it is 1333. It might be already advanced when you are setting the initial. You need to almost have the motor die, the last few flashes are the initial.

Right on Mbam! Also the V6-14 starts advancing at 650 rpm. I set mine at 28 total (blower motor), at idle, it falls in around 20-22

Set the total timing and see where the initail falls in.

Kurt

With initial advance around 12-14 degrees it idles at 900-1000rpm and sounds nice. With the initial set around 24-26 it idles around 1200 and dosen't sound like a relaxed, idling motor. As Mbam says, maybe it's already advanced, since my initial and total are the same.

While I could just set the total at 30-32, It dosen't seem right to have that much advance at that low rpm. Isn't that putting a lot of stress on the bottom end? I understand that when inertia comes into play from the higher rpm it doesn't matter, but it doesn't seem right for an idling speed. That's more of a question, not a statement. I'm new to all this stuff and certianly don't claim to be very knowlegable.

Maybe for my personal preferences, which may not involve extracting every last hp from the engine I should swtich to a V8-20 module. What are you opinions on how that would effect the situation. Also, rather than $250 for a module, wouldn't I be better off to just go with a new MSD distributor for about $350 and have a programmable advance curve?

Thanks for everyone's help who responds.

To answer if you should run a V6 modual or not, we need more details about your engine. Does it have a supercharger or a big cam?
The only reason to run the V6 is so there is less advance than the normal 20°-24° used on stock V8s.
If you have a basically stock 502 (500HP or less), run a V8 modual or buy a new ignition/distributor...

Normally aspirated motor with a cam upgrade that I'm told is as big as one can go with the stock valve train. With the IMCO powerflow exhaust I'd like to think I'm around 475hp. Anyone have a V8-20 I could borrow to help make the decision?

Pat, I look forward to meeting you. I met "full throtle" and "JRomy" at Cluadio's last Sunday. We (wife & 2 kids) plan on going to Block Island next weekend.

Cool, It's great to meet new people with similar interest.
The wife and I have two kids as well.
Where do you boat out of?
We keep our boat in Chester on the CT River...

Are you grounding out the purple/white wire while setting everything

That only applies to the Thunderbolt V system. He's got a T-IV