Need an New Ignition Amplifier? No Spark...........

[hezzy602]

I have a 1985 Mercrusier MCM 205 4.3 with the Thunderbolt IV Ignition.
The problem started on the water last summer. Turned off the boat, and when I tried to start it back up it just cranked and cranked. Let it sit for a lil and it started back up, that day no more problems. Next time on the water same thing, turned it off but wont start back up. Let it sit and started back up. Started to high tail it back to the dock and hit a good size wave and when the boat slammed back down to the water, DEAD in the water. Cranked for every no start. That was last summer no That i have time I am trying to fix.
So I started trouble shooting with a diagram I found on here about trouble shooting no spark. I have gotten to the step where it wants me to install a spark gap tester. BUt I do not have one, I am ordering one from amazon. But MY QUESTION IS the solution after this step is 1. replace the coil 2. replace ignition module 3. replace sensor in distributor.....I have already replaced the coil. still no spark.
When I test the new coil---from the two outside leads I get--1.1ohm-----from plug in the middle to the outside (-) lead i get---7.89k ohms
I have STARTED to look for a new thunderbolt ignition module. But can only find them USED. ****WHere Can I get a new thunderbolt or substitute it to a new system??**********
So until I get a spark gap tester any words from people with past problems???

 

[achris]

Re: Need an New Ignition Amplifier? No Spark...........

Instead of waiting for the gap tester, just get an old spark plug and open it up quite wide (about 1/4" will do). Lay it on the engine block and that will be your spark gap tester. I would use the high tension lead the runs from the coil, not one of the plug leads... In fact, what I'd do it get a longer lead in there so I can watch the spark gap better...

Then carry on your testing...

I would be suspect about a used amplifier... The original part# was 390-9355A2, has superseded to -15247T02, and it's not cheap!

Try one of the aftermarket mobs, or a complete replacement Voyager is cheaper -> http://www.michiganmotorz.com/delco-voyager-marine-electronic-distributor-p-121.html

Chris......

 

[hezzy602]

Re: Need an New Ignition Amplifier? No Spark...........

Instead of waiting for the gap tester, just get an old spark plug and open it up quite wide (about 1/4" will do). Lay it on the engine block and that will be your spark gap tester. I would use the high tension lead the runs from the coil, not one of the plug leads... In fact, what I'd do it get a longer lead in there so I can watch the spark gap better...

Then carry on your testing...

I would be suspect about a used amplifier... The original part# was 390-9355A2, has superseded to -15247T02, and it's not cheap!

Try one of the aftermarket mobs, or a complete replacement Voyager is cheaper -> http://www.michiganmotorz.com/delco-voyager-marine-electronic-distributor-p-121.html

Chris......

Holy crap those OEM parts aren't cheap huh. I guess if i have to I will just go with the aftermarket one, you think its any good??
I am going try out what you said tomorrow afternoon.

 

[achris]

Re: Need an New Ignition Amplifier? No Spark...........

... you think its any good??

I haven't tried one myself, but I've not heard any negative reports...

 

[ken303]

Re: Need an New Ignition Amplifier? No Spark...........

I have a 1985 Mercrusier MCM 205 4.3 with the Thunderbolt IV Ignition.
The problem started on the water last summer. Turned off the boat, and when I tried to start it back up it just cranked and cranked. Let it sit for a lil and it started back up, that day no more problems. Next time on the water same thing, turned it off but wont start back up. Let it sit and started back up. Started to high tail it back to the dock and hit a good size wave and when the boat slammed back down to the water, DEAD in the water. Cranked for every no start. That was last summer no That i have time I am trying to fix.
So I started trouble shooting with a diagram I found on here about trouble shooting no spark. I have gotten to the step where it wants me to install a spark gap tester. BUt I do not have one, I am ordering one from amazon. But MY QUESTION IS the solution after this step is 1. replace the coil 2. replace ignition module 3. replace sensor in distributor.....I have already replaced the coil. still no spark.
When I test the new coil---from the two outside leads I get--1.1ohm-----from plug in the middle to the outside (-) lead i get---7.89k ohms
I have STARTED to look for a new thunderbolt ignition module. But can only find them USED. ****WHere Can I get a new thunderbolt or substitute it to a new system??**********
So until I get a spark gap tester any words from people with past problems???
View attachment 155443

I have the same problem with my 89 4.3 LX. It stared with the engine cutting cruising above 3000 rpm, would usually it would stay running, above 3500 it would die. You could crank and crank and it seemed to fire when it wanted to.
Went thru the whole diagnostic process, replace cap and rotor(needed them) ign module, coil. Started seem to run fine, then quit again, no spark. Replaced coil wire, started, took it out ran fine for a while then started to cut out and stall.
Didn't want to start, pulled coil wire off dist cap, turned it over no spark.
Just for fun I unplugged the ign amplifier, plugged it back in and guess what fired up right away, drove the boat until it quit again, checked no spark,unplugged and plugged in the ign amp fired right up.
The odd thing is if you keep it under 3000 it runs fine.
Options for repair
1. $950.00 yes 950.00 in Toronto Ontario Canada
2. Performance Distributers all in one replacement marine dist. for around $300
Try to find one on EBay
Buy one in the US and pay the duty, would be a lot less then buying it here.

Try unplugging and plugging the ign amp to see if it will start
I went to to large marinas and was told that these never fail only sold 1 in 12 years
Good luck with yours
Ken

 

[Don S]

Re: Need an New Ignition Amplifier? No Spark...........

Personally, if I had problems with a Thunderbolt IV ignition module on a boat of mine, I would be installing a new Delco EST distributor in it in a heart beat. No way would I pay the stupid Merc prices for a module when the distributor kit with coil, and plug wires is less than that module.
It does take a bit of rewiring for Mercs with Alpha drives and the shift interrupt system, but you never have another 400 dollar (US) module go bad again.

 

[ken303]

Re: Need an New Ignition Amplifier? No Spark...........

Personally, if I had problems with a Thunderbolt IV ignition module on a boat of mine, I would be installing a new Delco EST distributor in it in a heart beat. No way would I pay the stupid Merc prices for a module when the distributor kit with coil, and plug wires is less than that module.
It does take a bit of rewiring for Mercs with Alpha drives and the shift interrupt system, but you never have another 400 dollar (US) module go bad again.

Update, I gave this problem alot of thought, why would the ICM work and then stop and when unplugged and plugged in again start working. Most weird electrical problems that I have seen on cars are caused by GROUND problems.
I had cleaned all the grounds and all positive connections, I checked the manual to make sure all the connections were correct, everything was correct.
I decided to add another ground wire from the grounding bolt for the ICM and the battery.
Took the boat out and it ran great any rpm no problems.
If anybody has similar problums I would suggest an aditional ground wire on the ICM and check the coil wire.
The lesson that I learned is that dealing with boats before you put it in the water clean every connection positive and negative, check the dist. cap and rotor, time spent doing this will definitly decrease problems.

 

[hezzy602]

Re: Need an New Ignition Amplifier? No Spark...........

Well I have tried a lot of what you guys are talking about, like checking for bad grounds. Still it just cranks and cranks, just missing that damn spark. I cant unplug the ign. amp. the wires are hard wired into it. I am down to "replacing ign. amp." on that diagram for trouble shooting. So I think I am just going order one of the aftermarket kits you guys are talking bout(new dist., wires, module, etc.).
So you say though that it can be a challenge wiring it in to you cut out switch??

Here's kinda a random question but when I was troubleshooting I was checking for continuity in my lead from the coil to the dist. and I got a very High ohm reading, so i figured I had a bad wire. but turns out all the spark plug wires read at a very high resistance. WHy is this? I would think it would just read zero?!?!

 

[hezzy602]

Re: Need an New Ignition Amplifier? No Spark...........

Well I have tried a lot of what you guys are talking about, like checking for bad grounds. Still it just cranks and cranks, just missing that damn spark. I cant unplug the ign. amp. the wires are hard wired into it. I am down to "replacing ign. amp." on that diagram for trouble shooting. So I think I am just going order one of the aftermarket kits you guys are talking bout(new dist., wires, module, etc.).
So you say though that it can be a challenge wiring it in to you cut out switch??

Here's kinda a random question but when I was troubleshooting I was checking for continuity in my lead from the coil to the dist. and I got a very High ohm reading, so i figured I had a bad wire. but turns out all the spark plug wires read at a very high resistance. WHy is this? I would think it would just read zero?!?!

................................

 

[nola mike]

Re: Need an New Ignition Amplifier? No Spark...........

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Don't know the specs for your engine, but spark plug wires can have significant resistance and be within specs.

 

[ken303]

Re: Need an New Ignition Amplifier? No Spark...........

Don't know the specs for your engine, but spark plug wires can have significant resistance and be within specs.

Yes depending on which manual or who is givivng you advice the range is usually 400 to 800 ohms per foot.
If I were you before spending anymore money, cut the wires going to the Ign amp, leaving enough to reconnect them and check each wire for continuity, if ok solder/connect them back together and run the ground directly to the battery. If it still doesn't work it would be a good idea to relplace the dist. all the company's I've researched provide the diagrams to wire th cut off switch.
Good luck