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Shimano Thunnus Ci4 Review

Shimano Thunnus Ci4 Review

Do you like lightweight reels and fishing with cut or live bait, but have a need for something larger than a 4000 series?

If you answered yes then this review of the Shimano Thunnus Ci4 Saltwater Spinning reel might be just what you have been looking for.

Shimano redesigned the popular Thunnus saltwater spinning reel in 2010 and replaced the aluminum body with the Ci4 carbon body to reduce the weight.

Shimano Thunnus Ci4 | Amazon

Seemingly against the laws of nature, lightweight with the power to stop big fish e not words commonly found together in a sentence.

Buy on Amazon
“Here at we participate in affiliate programs and may earn a commission if you make a purchase, at no additional cost to you.”

While the Thunnus was always a popular reel among serious anglers, the weight made it acceptable for boat fishermen but heavy for those wishing to fish all day long.

The Thunnus is a baitrunner reel which is primarily designed for live lining or chunking, however, due to its lighter weight, it is a good crossover reel that also works well for throwing plugs.  Here is a great article on baitrunner reels and how to use them.

The Bottom Line

  • Very versatile higher-end baitrunner design spinning reel for live/chunk bait and artificial lures
  • Very smooth reel with the baitrunner dual drag system
  • High level of manufacturing quality, parts are easy to find and reel is easy to maintain
  • Very durable and lightweight Ci4 composite body and rotor for strength

The Shimano Thunnus is my favorite higher-end baitrunner reel and is available HERE.


Super lightweight Ci4 frame and rotor – Both the frame and rotor are made of the very strong and super lightweight Ci4 carbon fiber composite material.  This equates to a reel that is 5oz – 7oz lighter than the original Thunnus models.

If you were wondering what the Ci4 stands for it is “Carbon Interfusion” and the 4 stands for the number of electrons in the carbon atom.  I am sure you feel much better now that you know that.  What it means for you is that the frame and rotor are both lightweight and very strong.

Paladin® Gears – Shimano uses a combination of a hardened brass pinion gear with a cold forged aluminum drive gear to deliver its legendary smoothness.  The combination of these two metals has been shown to have greater durability than a pure stainless steel drive train.

Propulsion® Line Management System – Shimano’s Propulsion Line Management System incorporates a special rolled lip design on the spool that allows the line to flow smoothly off of the spool during your cast.

After rigorous testing both in the field and with computer simulations, the lip design has proven to reduce the amount of friction that is caused by the spool lip during a cast.

What this means for you is that you can cast further and have less of a chance of both wind knots and backlashes.

Dyna-Balance® – When your car tire is out of balance you get wobble, the same can be said for the rotor on a spinning reel.  Shimano has started to use computers to aid in the balancing of each rotor to fine tune it and all but eliminate any wobble from the rotor.

Here again, is why Shimano continues to deliver silky smooth reels year after year.

Oversized Septon® Grips – The Septon grips seem to be a love-hate relationship with most anglers as they have a tendency to provide a really good grip (Love), but become sticky over time (Hate).

I have found that if I use a disposable lens cleaner wipe then I can get rid of the gunk and return the knob to its original tacky grip.

Waterproof drag with Dartainium® II cross carbon washers – Shimano uses their Dartanium dual drag system on the Thunnus which is the same drag as found on the Baitrunner D series of reels which is a cross carbon fiber drag system.

The cross carbon drag is very smooth from the time the hook is set all the way through the fight.

Dartanium drag washers have been reported to break down after a period of time, the drag washers have been known to smash down and actually delaminate and come apart.

While I have not personally experienced this, I wanted to bring it to your attention.  This is not a big deal as they can easily be swapped out with something like Carbontex Replacement Washers for about $12, just make sure to get the right size for your specific reel.

Front & Rear Baitrunner Drag – The dual baitrunner drag system on Thunnus means that you will have nearly unlimited control over the drag.  The front or top drag is adjusted on the top of the spool where the rear drag is adjusted on the bottom of the reel.  For more about Baitrunner Reels click HERE.

Six shielded A-RB® ball bearings – Shimano uses 6 of their shielded A-RB (anti-rust) bearings for a super smooth retrieve.  The anti-rust bearings are shielded on both sides to minimize the amount of water that can get to the bearings which means that you do not need to be as concerned with rust from our old friend Mr. Saltwater.

Super Stopper® II – The Thunnus comes with the Super Stopper II one-way roller bearing to assure that you get a smooth hook set.

Features at a Glance

  • Super lightweight Ci4 frame and rotor
  • Paladin® Gears
  • Propulsion® Line Management System
  • SR® one-piece bail wire
  • Power Roller® III
  • Direct Drive Mechanism
  • Oversized Septon® Grips
  • Waterproof drag with Dartainium® II cross carbon washers
  • Front & Rear Baitrunner Drag
  • Six shielded A-RB® ball bearings
  • Super Stopper® II

The Shimano Thunnus Ci4 is designed to be “The” best saltwater baitrunner reel on the market for those who are targeting larger species of inshore favorites such as Snook, Redfish, Tarpon, Shark, and Flounder to name a few.

I also like to use the Thunnus Ci4 when we go for grouper off the coast of Southwest Florida.  The rear drag allows me to set it very light and allows the live bait, usually pinfish to swim freely. We refer to this as live-lining.

Once the fish takes the bait, I just start the retrieve and the front or primary drag is set and the fight is on.

As you can see in the chart below the Thunnus comes in 4 models:

The Thunnus Ci4 4000 Model # TU4000CI4 – Great for your smaller inshore species but has enough line capacity to fight fish that love to run.

The Thunnus Ci4 6000 Model # TU6000CI4 – This size is great for medium inshore species such as large snook, reds and smaller sharks.

The Thunnus Ci4 8000 Model # TU8000CI4 – When going for Grouper, and large inshore species this is my pick.

The Thunnus Ci4 12000 Model # TU12000CI4 – When I need the extra drag and line capacity the 12000 fits the bill.

For those of you who want all the details I have provided the chart below.

ModelLine Retrieve (in)Mon Cap
Braid Cap
S-SUS BearingsMax Drag
Gear RatioWeight (oz)

The bottom line is that the Shimano Thunnus Ci4 is the top of the line baitrunner reel on the market.  With its lighter weight but still strong construction, it is a reel that you can use all day long without getting tired.

The infinite adjustability of the dual drag system is what makes this reel stand apart from the competition and it is super smooth.


  • Infinite adjustability of dual drag
  • Very lightweight while still strong
  • Very smooth all around


  • Higher price point


The obvious comparison would be the Shimano Baitrunner D.  What you need to understand is that the Baitrunner D, while a good quality reel and a lower price point by roughly $100, has a lower end gearing system and is a heavier reel.  Read the full Shimano Baitrunner D Review HERE.

Another reel to consider would be the Penn Spinfisher V in the Live Liner models.  There are 3 models that include the SSV4500LL, SSV6500LL and the SSV8500LL.  Read the full review of the Penn Spinfisher V Live Liner HERE.

In Conclusion

Overall if you have the budget and are looking for a high-quality and at the same time lightweight baitrunner style reel, the Shimano Thunnus Ci4, in my opinion, is a clear winner.

This is a reel that if well cared for, will last you season after season of low maintenance due to its high-quality gearing and bearing systems.

Shimano Thunnus Ci4 | Amazon

Seemingly against the laws of nature, lightweight with the power to stop big fish e not words commonly found together in a sentence.

Buy on Amazon
“Here at we participate in affiliate programs and may earn a commission if you make a purchase, at no additional cost to you.”

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