Stage 1 Kit (325HP) — Install Guide
Not for: 230 / 260 / 300 HP variants (use the matching Stage 1 kit for your HP rating). Not for 1503 4-TEC. Critical: Stage 1 is the entry point of the GT40...
GT40 Marine | SKU GT40-SD-STG1-325 | Stage 1 Performance Package | Rev 1.0 — 2026-05-24
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 the matching Stage 1 kit for your HP rating). Not for 1503 4-TEC. Critical: Stage 1 is the entry point of the GT40 performance pyramid. Stage 2 / Stage 3 / Stage 4 build on top of Stage 1 — you can not skip Stage 1 and install a Stage 2 kit on a stock craft without significant component overlap and tune calibration mismatch. Confirm hull and engine code (1630 ACE 325) before opening any packaging.
What Stage 1 Delivers
Stage 1 is the first measurable performance step on the 1630 ACE 325 platform:
- Power gain: approximately +10-15 HP over stock 325 HP rating, depending on conditions
- Throttle response: sharper off-idle and mid-throttle response from reduced intake/exhaust restriction
- Top speed: typically +2-4 mph over stock at sustained WOT
- Brand voice: Stage 1 owners hear and feel an immediate difference, but reliability remains at stock-equivalent levels
- Warranty implications: Stage 1 is the most conservative entry point — components are bolt-on, no ECU reflash required, no permanent engine modifications
Stage 1 Components (in the Kit)
This kit is a master sequence-document — each component has its own detailed install guide referenced below. Do not begin installation without reading each component guide in full first.
| # | Component | SKU | Detailed Guide |
|---|---|---|---|
| 1 | Carbon Fiber Cold Air Intake | GT40-SD-INT-CF | GT40-SD-INT-CF_COLD_AIR_INTAKE_KIT_INSTALL_GUIDE.md |
| 2 | Catch Can | GT40-SD-CC-4TEC | GT40-SD-CC-4TEC_CATCH_CAN_INSTALL_GUIDE.md |
| 3 | Intercooler Tubing + BOV | GT40-SD-TUBE-325-BOV | GT40-SD-TUBE-325-BOV_INTERCOOLER_TUBING_INSTALL_GUIDE.md |
| 4 | Ribbon Delete Kit (recommended at Stage 1, mandatory Stage 2+) | GT40-SD-RDK-SD300 | GT40-SD-RDK-SD300_RIBBON_DELETE_KIT_INSTALL_GUIDE.md |
Plus the following package-level items:
- (1) GT40 Stage 1 kit assembly hardware bag (combined hardware from all 4 component kits, pre-sorted by install step)
- (1) Stage 1 calibration confirmation card (no ECU reflash needed at Stage 1, but the card documents the date of build for future Stage 2/3 upgrade reference)
- (1) Stage 1 dyno-baseline form (optional — for owners who want to baseline their stock craft before install and compare post-install)
- (1) GT40 product registration card
- (1) This master guide
Verify each component sub-kit is complete before starting. Missing parts: support@gt40marine.com.
Tools Required
Full tool list across all 4 component installs:
- 8 mm / 10 mm / 13 mm / 17 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, 5–60 Nm range
- Long extension bars
- Hose-clamp pliers
- Marine-grade exhaust sealant applicator
- Drill + 3-1/8" hole saw (for ribbon delete, only if port not pre-cut)
- Flashlight or headlamp
- Shop towels — bring twice what you think you'll need
- Marine-grade copper anti-seize compound
- Trim removal tool (plastic pry)
Safety
Read the safety section of each component guide before starting. Aggregate safety summary:
- Battery disconnected for the entire Stage 1 build duration.
- Cold engine only. The supercharger, exhaust manifold, and J-pipe all retain heat for over an hour after operation.
- Eye protection mandatory for the entire build.
- Hand protection when handling exhaust components and ceramic-coated tubing.
- No smoking / open flame.
- Marine-grade install only. Stage 1 is designed for closed-cabin PWC engine bay use, not snowmobile or automotive application.
If you are not comfortable with the full Stage 1 build, take it to a certified marine technician. Stage 1 is a 4-8 hour install for an experienced DIY mechanic, 6-12 hours for a first-timer.
Recommended Install Sequence
Install order matters. Follow this sequence to minimize re-work:
Phase 1 — Engine bay preparation (15 minutes)
- Disconnect battery negative
- Remove seat, top hatch, storage bin
- Drain any residual coolant or fuel from recent runs
- Photograph all factory routing before disassembly
Phase 2 — Intake side (45-60 minutes)
- Install the Carbon Fiber Cold Air Intake (
GT40-SD-INT-CF) per its detailed guide - Test-fit the IAT and MAP sensor connections — these become harder to access once the intercooler tubing is in
Phase 3 — Charge / boost side (60-90 minutes)
- Install the Intercooler Tubing + BOV (
GT40-SD-TUBE-325-BOV) per its detailed guide - Pull-test every coupler before moving on
Phase 4 — Exhaust modification (60-90 minutes, includes 2-hour sealant cure)
- Install the Ribbon Delete Kit (
GT40-SD-RDK-SD300) per its detailed guide - Begin sealant cure timer — do not skip the 2-hour minimum cure before first start
Phase 5 — Catch can (30-45 minutes, in parallel with sealant cure)
- Install the Catch Can (
GT40-SD-CC-4TEC) per its detailed guide while the ribbon delete sealant cures - Verify the can sits below the breather port height — critical for proper oil separation
Phase 6 — Final assembly and first start
- Walk the entire engine bay — every fastener, every clamp, every hose, every electrical connector
- Reconnect battery negative (after the 2-hour sealant cure has fully elapsed)
- Replace seat, hatch, storage bin
- Start the engine on the trailer with the cooling hose connected
- Idle for 60 seconds — listen for any leak (exhaust, boost, or coolant)
- Bring engine to 3000 RPM briefly — verify no fault codes, listen for BOV operation, confirm the new exhaust note
- Scan with BUDS or compatible OBD diagnostic — no new fault codes
- After shutdown, visually inspect every joint in the engine bay
If clean: Stage 1 install complete.
Post-Install — Water Test
First water session
Plan a dedicated first-run session — no passengers, calm water, no scheduled time pressure.
- Launch on a quiet boat ramp
- Drift away from the ramp for 30 seconds at idle
- Apply throttle gradually to half — feel for any unusual response, listen for any leak
- After 5 minutes at part throttle, brief full-throttle pulls (5-10 second bursts)
- After 15 minutes total water time, return to dock
- Trailer out and inspect engine bay for any leaks or anomalies
If clean: Stage 1 break-in complete. Normal use thereafter.
What you should feel
- Sharper throttle response at low and mid-RPM
- Slightly louder exhaust note above 5000 RPM (from the ribbon delete)
- Improved acceleration in the 30-60 mph band
- Top speed gain of 2-4 mph over stock baseline
- No engine warning lights, no rough running, no unusual smells
If any of the above is missing or you feel something off, return to dock and inspect.
Stage 1 → Stage 2 / Stage 3 / Stage 4 Upgrade Path
Stage 1 is designed as the foundation for further performance upgrades. The components installed at Stage 1 carry forward — they do not need to be removed or replaced at higher stages.
- Stage 2 adds: matched ECU calibration (Magic Module or equivalent), supercharger pulley upgrade, fuel system upgrade
- Stage 3 adds: full Stage 3 exhaust kit (
GT40-SD-EXH-ST3), open loop cooling (GT40-SD-OLC-300), higher-flow injectors - Stage 3+ / Stage 4 adds: ported supercharger housing, custom calibration, intercooler upgrade, blower spacer
When upgrading from Stage 1 → Stage 2, only the calibration and pulley/fuel components are added. The intake, tubing, catch can, and ribbon delete from Stage 1 are reused as-is.
This staged path is why Stage 1 component quality matters — these parts will run on your craft for as long as the boat is in service, even after Stage 4 upgrade.
Post-Install Service Schedule
Stage 1 components require slightly more attentive service than stock parts due to the higher performance envelope:
| Interval | Task |
|---|---|
| First 10 hours | Re-torque all critical fasteners — see each component guide's torque summary |
| Every 25 hours | Inspect all hose clamps, coupler torque, and catch can drain valve |
| Every 50 hours | Drain catch can, inspect cooling water injection line, verify BOV operation |
| Every 100 hours | Replace catch can mesh, inspect ceramic coating on intercooler tubing, refresh exhaust sealant if any seepage visible |
| Annual | Full Stage 1 inspection — all components, all fasteners, all gaskets |
Document each service in a build log. When you upgrade to Stage 2 / 3 / 4, the build log accelerates the upgrade decision.
Troubleshooting (Master)
For component-specific troubleshooting, refer to each component guide's troubleshooting table. Stage 1-level common symptoms:
| Symptom | Likely Cause | Component Guide to Check |
|---|---|---|
| Lean stumble at high RPM | Boost leak in charge tubing | Tubing 325 guide, Step 5 |
| Check engine + IAT code | Intake sensor harness | Cold Air Intake guide, Step 6 |
| Oil pooling at valve cover | Catch can mounted incorrectly | Catch Can guide, Step 3 |
| Exhaust gas smell | Ribbon delete plate leak | Ribbon Delete guide, Step 5 |
| BOV doesn't open on lift | Vacuum reference line issue | Tubing 325 guide, Step 7 |
| Top speed unchanged | Calibration not matched to Stage 1 | Expected at Stage 1 (no ECU reflash) — gains are 5-15 HP without tune. Stage 2 adds calibration for full envelope |
| Cooling water not flowing to ribbon delete area | Not applicable — ribbon delete is dry side | N/A |
If symptoms persist after working through each component guide's troubleshooting, contact GT40 Marine support before further operation.
Warranty (Master)
GT40 Marine warrants the Stage 1 Kit components 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
- Damage from skipping any component install step (each component has its own warranty terms)
- Damage from operation outside design intent
- Damage from boost levels above the kit-rated ceiling on the Tubing + BOV component
- Damage from operation without proper cooling water flow
- Use on craft outside the listed fitment matrix
Per-component warranty terms apply per each component guide. The Stage 1 master warranty is the union of the individual component warranties — whichever protects the customer best applies.
To submit a warranty claim: email support@gt40marine.com with order number, photographs of the installed Stage 1 build, the build log entry from the install, 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 Stage 1 master 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.
- Dry-fit every hose before tightening clamps.
- Run and inspect for leaks at idle before loading the cooling system hard.
- Routing hoses where they rub under load
- Reusing weak clamps on pressure-side cooling lines
- Skipping leak check before the first ride