Stage 1 Kit (325HP) — Install Guide

GT40 Marine | SKU GT40-SD-STG1-325 | Stage 1 Performance Package | Rev 1.0 — 2026-05-24

Fitment

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

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 |

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

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.

Stage 1 Kit (325HP) — Install Guide

GT40 Marine | SKU GT40-SD-STG1-325 | Stage 1 Performance Package | Rev 1.0 — 2026-05-24

Fitment

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

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 |

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

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