Idles great / misses when throttled up

[achris]

Looked for it this morning - I must of lost it can you send it to me via email ? Dave95299@gmail.com

How Mercruiser Thunderbolt ignition systems work.

Mercruiser Thunderbolt ignition systems. Mercruiser introduced the Thunderbolt IV onto their engines in 1982, alongside the introduction of the 1-R drives. The TB-IV system was used until the introduction of TB-V mid-way through 1996. Thunderbolt V was an improvement on an already exceptionally...

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[kinger952]

Gauge on comp tester is bad !! Re did check this am. All above 150 lbs per cyl. Thank you

 

[itsathepete]

Did you figure why you lost spark? I suspect it's the same reason you have a misfire

 

[kinger952]

No I've been working on it when ever I get 10 here and there swapped coils still no spark. I have pickup in distributor coming

 

[Scott06]

No I've been working on it when ever I get 10 here and there swapped coils still no spark. I have pickup in distributor coming

Did you go through the trouble shooting guide chris posted ? This will identify if your sensor/ pickup is bad or module etc.

 

[kinger952]

Have not had a chance to really understand it but I will
I have a dist pickup coming for $19 shipped will try that 1st

 

[Scott06]

Have not had a chance to really understand it but I will
I have a dist pickup coming for $19 shipped will try that 1st

its your show but do the trouble shooting first if you can set points you can handle through the trouble shooting guide. No sense replacing the sensor if the module is at fault …
you have to remove the rotor and trigger wheel attached to it to get the sensor out. last TB rotor i removed was loctited down and didn’t come off without breaking.

 

[nola mike]

Looked for it this morning - I must of lost it can you send it to me via email ? redacted

Bad idea to put your email out here. The troubleshooting info is in the adults only section. @achris

 

[achris]

Have not had a chance to really understand it but I will
I have a dist pickup coming for $19 shipped will try that 1st

$19? That's not OEM... Bad idea. Let me quote you something...

I took the carb apart and found that the needle was stuck in the seat. Brand new parts.

As everyone told me, ONLY buy OEM kits. I ordered a cheap one off Amazon

Judging by comments on this forum regarding 'cheap' parts, you've got less than 50% chance of them being any good. I had a friend have a water pressure sensor fail. Ordered a cheapie off ebay, dead out of the packet.

I know genuine parts are stupidly priced, and I hate giving Merc any more money or credit than they deserve, but for most things, their QC is by far the best. Just to let you know, all those aftermarket part are made, not only in the same factory as the genuine, but on the same line, as the same time. Once a run is done, QC go through and weed out the ****, toss it aside and the cream is bought by Merc. The other stuff isn't thrown out, it's sold the aftermarket sellers. It's what Merc reject that the others sell. Little wonder it's got such a high failure rate.

Chris.......

 

[dubs283]

I hate giving Merc any more money or credit than they deserve

jaded

 

[achris]

jaded

 

[nola mike]

$19? That's not OEM... Bad idea. Let me quote you something...


Judging by comments on this forum regarding 'cheap' parts, you've got less than 50% chance of them being any good. I had a friend have a water pressure sensor fail. Ordered a cheapie off ebay, dead out of the packet.

I know genuine parts are stupidly priced, and I hate giving Merc any more money or credit than they deserve, but for most things, their QC is by far the best. Just to let you know, all those aftermarket part are made, not only in the same factory as the genuine, but on the same line, as the same time. Once a run is done, QC go through and weed out the ****, toss it aside and the cream is bought by Merc. The other stuff isn't thrown out, it's sold the aftermarket sellers. It's what Merc reject that the others sell. Little wonder it's got such a high failure rate.

Chris.......

I'll roll the dice if it won't leave me stranded or if the labor involved in redoing it isn't bad. I've had plenty of good luck with aftermarket parts over the years... Although it seems like there's a lot more super cheap crap around now that wasn't there even 10 years ago

 

[kinger952]

Rotor came off fairly easy - I'm thinking of switching both distributors out for HEI type in which I have tons of experience with super easy to diagnose !! Very easy to install and wire in and easy to hook up advance and adjust . But will see if pickup is at fault I've tested coils 1 is acting funny so I will find a good one I know I have a good one in garage and will try that one . so my next step is pickup in distributor for now - taking a break for a day and going out for a motorcycle ride to air out my brain what's left of it that is
Thanks for the help

 

[Rick Stephens]

Rotor came off fairly easy - I'm thinking of switching both distributors out for HEI type in which I have tons of experience with super easy to diagnose !!

Make sure marine rated. Not sure there even is an HEI ignition that is marine rated. And it is important.

 

[Scott Danforth]

Yes I have between 105 and 112 all 8

this is still the issue unless the gauge was crap

 

[Scott06]

Rotor came off fairly easy - I'm thinking of switching both distributors out for HEI type in which I have tons of experience with super easy to diagnose !! Very easy to install and wire in and easy to hook up advance and adjust . But will see if pickup is at fault I've tested coils 1 is acting funny so I will find a good one I know I have a good one in garage and will try that one . so my next step is pickup in distributor for now - taking a break for a day and going out for a motorcycle ride to air out my brain what's left of it that is
Thanks for the help

Good , yes burn some gas … i do the same with my GTO.

You will find the TB doc Chris sent that the the diagnosis is very very simple as well. The TB is essentially an merc designed HEI system. Not as commonplace as the GM hei is in the auto world but every bit as good a system.

Out of all the engines I’ve maintained the TB has the hottest spark I ever worked with nice blue spark on gap tester Only downside is the cost of the merc proprietary module if it dies , I bought a spare on eBay for 200 to hedge my bets

 

[kinger952]

this is still the issue unless the gauge was crap

Gauge was CRAP totally wrong used new one !!! N.I B.

 

[kinger952]

Good , yes burn some gas … i do the same with my GTO.

You will find the TB doc Chris sent that the the diagnosis is very very simple as well. The TB is essentially an merc designed HEI system. Not as commonplace as the GM hei is in the auto world but every bit as good a system.

Out of all the engines I’ve maintained the TB has the hottest spark I ever worked with nice blue spark on gap tester Only downside is the cost of the merc proprietary module if it dies , I bought a spare on eBay for 200 to hedge my bets

I'm still debating on it ? and looking for a module but not what some folks are asking ( above 300 ) I can wait specially when fuel is over $7 a gallon and this thing uses 46 per hr. W.F.O
The module is the older style the bigger box type on one engine ( alum housing) and on the good runner is a newer style of plastic with the plug in on the module itself. If I could change over to the newer style for a reasonable cost I probably would go that route am going to kinda look into it