1-805-484-2992
Quotes - Engineering - SalesCAT 3408 Heat Exchanger
V8 propulsion and the space it leaves
The 3408 puts eight cylinders where a six used to sit, and in most hulls that means the cooling hardware is packed tight against the block or the outboard stringer. When a 3408 jacket water cooler fails, half the job is heat load and the other half is envelope: what will physically go back in without rerouting hoses or moving a bracket the yard glassed in twenty years ago.
Marine 3408 ratings are widely published in the region of 400 to 900 horsepower depending on generation and duty class. As with every engine here, we do not treat that as one number. The jacket water heat rejection comes from the engine data sheet for your specific rating, and that with the design seawater inlet temperature sets the surface area. The available raw water flow then decides whether the selection runs two pass or four.
Send us the engine serial and rating, a photo of the plate on the existing cooler or the old part number, the connection sizes and thread type, and the measured envelope you have to work in. A CAT 3408 heat exchanger replacement is normally built with copper-nickel tubes, bronze bonnets and zinc anodes, with titanium tubes optional. Call 1-805-484-2992 or email Sales@HeatX.com.
Jacket Water
Yacht Installations
Clearance Checked
Gear Oil Cooling
Fitting A 3408 In The Space Available
Envelope and duty are checked together so the replacement goes back on the existing brackets and piping.
Duty Inputs
- Rating and duty class
- Jacket water heat rejection for the rating from the data sheet
- Design seawater inlet temperature
- Raw water flow at the cooler
- Coolant flow through the shell
Envelope
- Shell outside diameter
- Overall length across bonnets
- Connection positions and orientation
- Mounting centres and bracket type
- Clearance for bundle withdrawal
Duty Profile
- Seawater on the tube side
- Coolant on the shell side
- Two pass where flow is generous
- Four pass where flow is limited
- Marine option set BR-CN-B-Z
| MODEL / RATING | HORSEPOWER | DUTY | TYPICAL SELECTION |
| 3408 naturally aspirated | About 400 to 500 HP | Continuous propulsion | HC Series mid frame |
| 3408 turbocharged marine | About 500 to 700 HP | Intermittent propulsion | HC Series, longer shell |
| 3408 high output | About 700 to 900 HP | Planing hull propulsion | HC Series upper frames |
| 3408 auxiliary or genset | About 400 to 600 HP | Prime power | AB Series fixed tube |
| Reduction gear oil | Sized on oil load | Gear oil cooling | Reduction Gear Cooling |
The V8 Layout And Cooler Placement
Why 3408 installations are tight
A V8 is wider than the inline sixes many hulls were originally built around, and on a repowered boat the cooler often ended up wherever there was room rather than where it should ideally sit. That legacy shows up when the unit is replaced: connection orientation and bonnet clearance can matter more than shell length, because the hoses are fixed and the bracket is not moving.
We ask for the measured envelope on 3408 enquiries for that reason. Given the space and the duty we can usually reach the required surface with a different combination of shell diameter and length, or by changing the pass arrangement, rather than forcing a longer unit into a bay that will not take it.
Two coolers, one service history
Most 3408 boats run a pair. Both engines have seen the same water, the same duty cycle and the same neglected zincs, so when one cooler fails the other is usually within a season of the same fate. Replacing both while the boat is opened up costs one labour bill instead of two.
It also gives you a matched pair, which matters when you are trying to diagnose an imbalance later. If you are quoting a pair, tell us and we will make sure both units carry identical option sets, connection schedules and anode arrangements.
Related
HEAT EXCHANGERS • PARTS
Tube Bundles
Replacing the bundle where the shell is still sound
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VESSELS & ENGINES • BY VESSEL
Yachts And Sportfishers
Tight engine bays and the coolers that have to fit them
+ Learn MoreCommon FAQs
Often not, which is why we ask for the measured envelope. Where length is limited we can usually reach the same surface area with a larger shell diameter or a different pass arrangement. Send the space you have along with the rating and we will work inside it rather than around it.
Marine 3408 ratings are widely published in the region of 400 to 900 horsepower depending on generation, aspiration and duty class. That spread is wide enough that the jacket water load differs substantially across it, so we size from the rating on your engine and the heat rejection on that data sheet.
Usually yes. Both engines have run the same water, the same hours and the same zinc replacement schedule, so a failure on one is a fair warning on the other. Replacing both during a single haul-out costs one labour bill and leaves you with matched units.
Yes. Gear oil coolers are sized on oil heat load, oil grade and allowable pressure drop. If it shares the raw water header with the jacket water cooler, tell us the whole circuit so the flow and pressure drop budget is shared properly between the units on it.
Enough beyond one bonnet to withdraw the full tube length, which on these frames can be substantial. Where the bay will not allow it, a shorter shell with a larger diameter is often the answer. Note the actual clearance you have when you send dimensions and we will select accordingly.
