Thunderbolt or Thunderbolt V ?

Fishstick1962

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I have a 1998 4.3 carb'd mercruiser SN 0L051****. Can't remeber exactly. The cover over the spark arrester says that it is a Thunderbolt ignition system and that "Special timing procedures are required". My srevice manual only gives procedures for the Thunderbolt "V" ignition syst. The steps say to ground the purple/wht wire and set base timing. I cant find where the purp/wht wire ends. One end is in a connector attached to the unit. I cant find the other end. Is it loose and just wrapped up in the harness or does it terminate somewhere else? Or do I disconnect the connector and ground it from there? The book is not real clear on this. And... do I have a T'bolt or a T'bolt "V" ignition syst? Thanks in advance!
 

Bondo

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Re: Thunderbolt or Thunderbolt V ?

Ayuh,...... You've got the T-Bolt V,......
And you Only need the end of the Wire that you've already found......

Don will be along shortly,+ Probably has a Picture to clear things up for you.........
 

Fishstick1962

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Re: Thunderbolt or Thunderbolt V ?

Thanks Bond-O. I will unwrap the harness and find the loose end. Just didn't want to start opening things up if I didn't need to.
 

Don S

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Re: Thunderbolt or Thunderbolt V ?

Don't start taking the harness apart. That shouldn't be necessary. You need to read these instructions before doing anything.

TB5%20timing%20instructions.png
 

Fishstick1962

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Re: Thunderbolt or Thunderbolt V ?

Don s:
Thanks for the info. I followed your directions and she is purring like a kitten! NEVER ran this good before. I have the Mercury shop manuals and these steps are not outlined like yours are. Which manuals do you have, and can I buy them somewhere? Unless I was looking in the wrong place, my book only gave a vague discription of procedure. Again, thanks for the help!
 

Bondo

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Re: Thunderbolt or Thunderbolt V ?

Which manuals do you have,

It says Manual #24 right at the top of Don's picture........
 

Don S

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Re: Thunderbolt or Thunderbolt V ?

Manual 24 is for V8's, but the process is the same for V6's. Of course it's also outlined just like that in the V6 manual. Being as your's has an OD serial number you wouldn't even have a TBV ignition, only a TB4 and the engine would be 88 to 92. So you really need to find out what your SN actually is cause you are right at that changeover year of 98 and could have either a 98 or a 97 engine. Just depends on which as to which manual you SHOULD have. What MERC manual do you now have?
 

Fishstick1962

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Re: Thunderbolt or Thunderbolt V ?

I have manual 25. I went back and read them again. All the same info is there, just need to be smart enough to READ all of the notes and follow each step in order. But my book didn't tell me where the end of the pupl/wht wire was hiding. Yours does. And yours has a Big note about grounding the wire BEFORE starting the engine. BTW I put her in the water yesterday and she ran like a scalded dog!!! NEVER had that much power before! Thanks again DonS. Your help has been invaluble.
 

Don S

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Re: Thunderbolt or Thunderbolt V ?

You're going to hate this, but look at page 1B-27 of your #25 manual.
 
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