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Points to electronic ignition

3.0 is a inline four cylinder and the 4.3 is a V-6 two complete different animals. What do you have and or what are you looking to accomplish?
 
First off....... I'd not let electronic ignition or NO electronic ignition determine whether or not you would purchase the boat that you like.
In most cases, an electronic triggering ignition system can be added.


I am thinking that Mercruiser introduced their ThunderBolt IV ignition system in the early 80s.
ThunderBolt is often refered to as TB in the IV or V versions.
Merc's ThunderBolt systems are EST...... (electronic spark timing)


This has been borrowed from another boating forum. I can only assume that it is accurate:

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 reliable and well performing system. TB-IV modules were programmed with each specific engine’s own timing curve.

The modules started out as a large box mounted to the (usually) Port exhaust elbow.

In most write-ups that you'll find, they DO NOT go into detail as to how the system actually works.

Other than the indexing of the housing, the distributor itself has no advancing capability.
The distributor shaft is indexed to camshaft @ 1:1, meaning that the triggering event is fixed.
Since it's fixed, and since we can't create a spark event any sooner than the triggering event occurs, the triggering event must occur at/near the full spark advance potential.
It then relies on the algorythm and electronic programing of the ignition module to delay the spark event.
The delay is then altered as per engine RPM.
This means that the entire advancing curve (minus BASE advance) is turned over the electronic module!


Today, most (if not all) Marine ignition systems are EST.
 
The V6 was not introduced until ~'83

some of the early models had point ignitions

but I would say by '84/'85 they all had thunderbolt IV

also the early V6's were not counter balanced and had if I remember correctly a different firing order. These engines tended to vibrate at idle and there was nothing one could do to stop this.
when the counterbalanced V6's appeared in the late '80's then they became a great configuration. Smooth running!!

It was also around that time they went to electric fuel pumps as the GM blocks did away with the mechanical fuel pump on there production engines.



So if a V6 is what you decide make sure it is late 80's for the best configuration.

The 4 cylinders stayed points until the mid '90s.............only thing that changed was the cubic inches and horse power.........After the mid 90's they went with an electronic ignition also.
 
Why do you think they called it "Thunderbolt"? Thunder does not "bolt". Lightning does! Why not "LightningBolt" ignition? That would make far more sense to me. Lightning is definitely the phenomenon, and thunder is simply a by-product.
 
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