Cold Air Intake Kit (325HP) — Install Guide

GT40 Marine | SKU GT40-SD-INT-325 | 325HP Cold Air Intake + Airbox Removal | Rev 1.0 — 2026-05-24

Before You Start — Decision Tree

This install differs from the general carbon-fiber intake (GT40-SD-INT-CF) because the 325HP platform requires airbox removal, electronics relocation, and (in many cases) ECU mounting changes. Answer these questions before opening any packaging:

| # | Question | If yes | If no |

|---|---|---|---|

| 1 | Is your engine the 1630 ACE 325 (2024+ RXP-X / RXT-X / 2025+ GTX Limited)? | Continue | Use GT40-SD-INT-CF for 230/300, or contact support |

| 2 | Do you already have a GT40 catch can installed? | Skip catch-can step | This kit assumes a catch can — recommend installing GT40-SD-CC-4TEC first |

| 3 | Are you still running the OEM airbox? | Full airbox-removal procedure applies | Skip Step 3 |

| 4 | Have you already relocated the ECU for a tuner install? | Skip Step 6 ECU section | Plan additional 20 minutes for ECU relocation |

| 5 | Are you running a Stage 2+ tune? | Pair this intake with the matching calibration | Stock-tune install is fine — modest gain expected |

Confirm hull HIN year (2024+ on RXP-X/RXT-X, 2025+ on GTX Limited) and engine displacement (1630 ACE 325HP) before proceeding.

Fitment

| Platform | Model | Year | Engine |

|---|---|---|---|

| Sea-Doo | RXP-X 325 | 2024–present | 1630 ACE 325 |

| Sea-Doo | RXT-X 325 | 2024–present | 1630 ACE 325 |

| Sea-Doo | GTX Limited 325 | 2025–present | 1630 ACE 325 |

Not for: 230 / 260 / 300 HP variants (use GT40-SD-INT-CF). Not for 1503 4-TEC. Confirm engine code stamped on the block reads "1630 ACE 325" before install.

In the Box

• (1) GT40 high-flow filter housing, carbon fiber, gloss finish
• (1) High-flow air filter element, pre-oiled
• (1) GT40 325-specific intake adapter, billet aluminum, anodized black
• (1) Silicone coupler, 3.5" ID, reinforced charge-grade
• (2) T-bolt clamps, stainless 3.5"
• (1) Sensor harness extension, 12 inch
• (4) M6 × 25 mm SHCS — intake adapter mounting
• (4) M6 stainless flat washers
• (1) ECU relocation bracket (zinc-plated stainless)
• (2) M8 × 30 mm SHCS — ECU relocation bracket
• (2) M8 stainless flat washers
• (1) Coolant reservoir clearance shim kit (two 3 mm aluminum spacers + extended-length M6 hardware)
• (1) Install hardware bag — spare clamps, spare washers, two extra zip ties
• (1) Catch can vacuum reference tee fitting, brass (if your catch can does not already have a 325-compatible vacuum source)
• (1) GT40 product registration card
• (1) This guide

Verify all components present before starting. Missing parts: support@gt40marine.com.

Tools Required

• 8 mm / 10 mm / 13 mm sockets + ratchet, 3/8" drive
• T25 + T30 Torx drivers
• 4 mm + 5 mm + 6 mm hex (Allen) keys
• 1/4" + 3/8" drive torque wrenches, 5–25 Nm range
• Long extension bars (the 325 engine bay is tighter than the 230/300 — extension reach matters)
• Hose-clamp pliers
• Flashlight or headlamp
• Shop towels
• Trim removal tool (plastic pry)
• Marine-grade dielectric grease (small dab for sensor reconnects)
• Voltmeter or test light (for verifying ECU power continuity after relocation)

Safety

Read in full before starting.

1. Battery disconnected for the duration of the install.
2. Cold engine only. The 325HP supercharger and intake plenum hold heat after operation.
3. Eye protection when removing existing intake hardware.
4. No smoking / open flame.
5. ECU handling caution. The 325 ECU is more thermally sensitive than 230/300 platforms — do not place the ECU on metal surfaces, do not allow static discharge, ground yourself before handling.
6. Marine-grade install only. Not for snowmobile or automotive application.
7. 2-hour install window minimum. Do not rush — 325 intake work is more involved than a typical CF intake swap.

If you are not comfortable with PWC engine bay work that includes ECU handling, take the install to a certified Sea-Doo / BRP marine technician.

Pre-Install Checklist

• [ ] Watercraft on stable trailer or stand, drain plugs out
• [ ] Battery negative disconnected and isolated
• [ ] Engine bay clean and dry
• [ ] All factory torque values reviewed (see Torque Reference Summary at end)
• [ ] Pre-disassembly photographs taken — particularly the airbox routing, ECU mount location, and coolant reservoir clearance
• [ ] Catch can present and operational — this kit assumes you have one (the 325HP platform's PCV breather flow rate exceeds what a catch-can-less setup can manage cleanly)
• [ ] ECU relocation bracket pre-fit checked against the engine bay's port-side mounting surface

Step-by-Step Install

Step 1 — Access the Engine Bay

Remove the seat. On 2024+ RXP-X / RXT-X, also lift the storage bin to expose the engine compartment top hatch. On 2025+ GTX Limited, the front service hatch must be opened separately.

Disconnect the battery negative terminal. Secure the cable away from the post.

Step 2 — Identify the 325-Specific Layout

The 1630 ACE 325 engine bay layout differs from the 230/300 in three critical ways:

• The factory airbox is larger to accommodate the higher boost airflow — removal exposes more chassis area
• The ECU mounting bracket sits inboard on the airbox-side of the engine — the new GT40 intake adapter occupies that real estate
• The coolant reservoir sits 10 mm closer to the intake side on 325 craft than on 300 craft — clearance is tight without the supplied shim kit

Photograph everything in this state. You will reconnect to the same sensors but the ECU and coolant reservoir geometry may change.

Step 3 — Remove the Stock Airbox (325-Specific Procedure)

1. Unplug the IAT sensor — squeeze the plastic retainer, pull straight off
2. Unplug the MAP sensor harness from the airbox upper tab
3. Disconnect the secondary ground strap from the airbox-mounted ground point (this ground point relocates to the new GT40 adapter)
4. Loosen the airbox-to-supercharger clamp using an 8 mm socket
5. Remove the four M6 SHCS securing the airbox to the engine bracket (the 325HP airbox has 4 mounting points, not 3 like the 230/300 — 5 mm hex key)
6. Lift the airbox up and out. The rubber elbow comes with it.
7. Important: the 325 airbox often carries a small wiring harness for the supercharger boost solenoid — that harness STAYS in the engine bay. Trace it carefully before lifting.

Store the stock airbox if you may sell the craft in stock form later.

Step 4 — Pre-Fit Check on Coolant Reservoir Clearance

Before installing the new intake adapter, verify clearance:

1. Hold the GT40 325-specific intake adapter in its install position (against the engine bracket's 4 mounting bosses)
2. Verify minimum 8 mm clearance between the adapter and the coolant reservoir
3. If clearance is below 8 mm: install one of the supplied 3 mm aluminum shims between the adapter and the engine bracket on the inboard mounting bosses (uses extended-length M6 hardware from the kit)
4. Re-verify clearance after shim install

This pre-fit check prevents thermal expansion contact during operation — without the shim some craft will have the adapter rubbing the coolant reservoir at full boost temperature.

Step 5 — Install the GT40 Intake Adapter

1. Apply marine anti-seize to all 4 M6 × 25 mm SHCS threads
2. Position the adapter against the engine bracket, with shims installed if Step 4 indicated
3. Thread all 4 M6 SHCS through the adapter with flat washers — hand-tight only initially
4. Snug all 4 in a cross pattern
5. Torque to 10 Nm (89 in-lb) in two passes with a 5 mm hex socket

Step 6 — ECU Relocation (if applicable)

If your craft is stock-configured (ECU on the OEM airbox-side bracket), the ECU needs to move 50 mm port-side to clear the new intake adapter.

1. Locate the ECU — black plastic enclosure with multi-pin harness, secured by 2 M6 fasteners
2. Photograph the harness routing and connector orientation BEFORE disconnecting
3. Disconnect the ECU main harness (release the latch tab, pull straight off — do not rotate)
4. Remove the 2 M6 fasteners securing the ECU
5. Lift the ECU clear of the engine bay
6. Position the supplied ECU relocation bracket against the port-side mounting bosses (the 325 engine bay has pre-drilled relocation points — they're not labeled but are visible as 8 mm tapped holes on the port-side sidewall)
7. Thread the 2 M8 × 30 mm SHCS through the bracket with flat washers
8. Torque to 18 Nm (13 ft-lb)
9. Place the ECU on the new bracket — orient the harness connector in the same direction as the original install
10. Reconnect the ECU harness — listen for the latch click
11. Verify the harness has no strain at full suspension articulation (RXP-X has minimal articulation but always check)

Step 7 — Install the Carbon Fiber Filter Housing

1. Slide a T-bolt clamp onto each end of the supplied 3.5" silicone coupler
2. Push the coupler onto the supercharger inlet first — seat fully against the inlet shoulder
3. Push the other end onto the GT40 intake adapter outlet
4. Orient both clamp heads to a position you can reach with a torque wrench
5. Torque both T-bolt clamps to 5 Nm (44 in-lb) alternating until even
6. Pull-test the coupler — it should not move on either fitting
7. Slide the carbon fiber filter housing over the GT40 adapter neck
8. Tighten the housing clamp to 5 Nm (44 in-lb) — uniform draw, no clamp ear gap
9. Confirm housing clearance from chassis members: 10 mm minimum on all sides
10. Confirm the filter element is seated fully against the housing internal flange

Step 8 — Transfer Sensors and Connect Catch Can Vacuum

1. Remove the IAT sensor from the discarded stock airbox using a 10 mm socket
2. Apply a thin dab of dielectric grease to the sensor threads
3. Thread the IAT sensor into the threaded boss on the GT40 adapter
4. Torque IAT to 8 Nm (71 in-lb)
5. Reconnect the IAT harness — listen for the retainer click
6. Reseat the MAP harness retainer onto the new adapter mounting tab. If routing is tight, use the supplied 12 in. harness extension
7. Catch can vacuum reference: if your existing catch can does not have a 325-compatible vacuum reference port, install the supplied brass tee fitting inline on the vacuum reference line between the manifold port and the catch can. Use spring clamps on each side.

Step 9 — Reassembly and First Start

1. Walk the engine bay — every harness retainer, every clamp, every fastener torque, every ECU connector
2. Confirm no tools, rags, or removed hardware remaining
3. Reconnect the battery negative terminal — torque to 10 Nm (89 in-lb)
4. Verify ECU power-on: turn key to ACC, confirm dash illumination is normal, no fault codes on initial wake
5. Replace the engine bay top hatch, storage bin, and seat
6. Connect the cooling flush hose
7. Start the engine on the trailer
8. Idle for 60 seconds — listen for any intake leak (rush of air, lean stumble)
9. Scan with BUDS or compatible OBD diagnostic — confirm no new fault codes (P0102, P0107 indicate sensor reconnect issue; P0606 indicates ECU communication issue from improper relocation)
10. Bring engine to 3000 RPM briefly — confirm smooth response

If clean: install complete.

Post-Install

Break-In

Filter element is pre-oiled. No break-in cycle required. First 30 minutes of on-water operation may show slightly richer idle as the ECU adapts trim to the 325-specific intake flow profile — this is normal.

Tuning

This intake is plug-and-play with the factory 325HP calibration. Modest gain on a stock tune (8-12 HP).

For Stage 2 / Stage 3 / Stage 4 builds, pair with the matching GT40 calibration. The 325 intake delivers its full envelope only with a matched tune.

Filter Service

• Inspect every 25 hours
• Clean per filter manufacturer guidance — solvent wash + re-oil
• Replace at 200 hours or sooner if visible damage

ECU Relocation Verification

After 10 hours of operation, re-verify ECU bracket torque to 18 Nm. Hull vibration during the break-in period can loosen the relocation bracket — this is the only fastener in the kit that typically benefits from a re-torque.

Troubleshooting

| Symptom | Likely Cause | Fix |

|---|---|---|

| Lean idle / stumble at low RPM | Coupler not seated on supercharger inlet | Recheck Step 7 |

| Check Engine + P0102 | IAT harness not fully clicked | Reseat retainer |

| Check Engine + P0107 | MAP harness pinched or unseated | Reroute and reseat |

| Check Engine + P0606 | ECU relocation harness improperly seated | Disconnect, inspect pins for damage, reseat |

| Whistling above 4000 RPM | T-bolt clamp under-torqued | Retorque to 5 Nm |

| ECU bracket loose at 10-hour check | Normal break-in loosening | Re-torque to 18 Nm |

If symptoms persist after the checks above, contact GT40 Marine support before further operation.

Torque Reference Summary

| Fastener | Torque |

|---|---|

| Intake adapter to engine bracket M6 SHCS (all 4) | 10 Nm / 89 in-lb |

| ECU relocation bracket M8 SHCS (both) | 18 Nm / 13 ft-lb |

| Silicone coupler T-bolt clamps | 5 Nm / 44 in-lb |

| IAT sensor into adapter | 8 Nm / 71 in-lb |

| Filter housing clamp | 5 Nm / 44 in-lb |

| Coolant reservoir clearance shim M6 (if used) | 10 Nm / 89 in-lb |

| Battery negative terminal | 10 Nm / 89 in-lb |

All torque values nominal — refer to current Sea-Doo factory service manual for any conflicting OEM specifications.

Warranty

GT40 Marine warrants this kit free from defects in materials and workmanship for ninety (90) days from date of purchase. Warranty covers replacement of defective GT40-supplied components. Warranty does not cover:

• Damage from improper installation (particularly ECU handling — static discharge damage is not warranted)
• Damage from operation outside factory ECU calibration limits without supporting modifications
• Damage from operation without proper catch-can support
• Damage from operation without the supplied coolant reservoir shim where clearance required it
• Normal wear of consumable items (filter element)
• Use on craft outside the listed fitment matrix (any non-325HP engine)

To submit a warranty claim: email support@gt40marine.com with order number, photographs of the installed kit, and a description of the failure mode. Response within two business days.

Support

• Email: support@gt40marine.com
• Site: gt40marine.com
• Install help: include the GT40 SKU above and your hull serial number in any support correspondence

Built in the United States. Designed for buyers who want the best.

This guide is © 2026 GT40 Marine. All rights reserved.