RXP-X 300 Rear Exhaust Kit (2016–2019) — Install Guide

GT40 Marine | SKU GT40-SD-EXH-RXPX300-1619 | Stainless Rear Exhaust + J-Pipe Delete | Rev 1.0 — 2026-05-24

Fitment

| Platform | Model | Year | Engine |

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

| Sea-Doo | RXP-X 300 | 2016 | 1630 ACE 300 |

| Sea-Doo | RXP-X 300 | 2017 | 1630 ACE 300 |

| Sea-Doo | RXP-X 300 | 2018 | 1630 ACE 300 |

| Sea-Doo | RXP-X 300 | 2019 | 1630 ACE 300 |

Not for: RXP-X 300 model year 2020 or later (hull geometry changed in 2020 — different kit required). Not for RXT-X, GTX, or Wake Pro variants (those use GT40-SD-EXH-ST3). Not for 325HP. Confirm model year on the hull HIN before install — the 2019/2020 transition is the critical cutoff.

In the Box

• (1) GT40 stainless steel rear exhaust outlet, hand-formed, mirror-polished
• (1) GT40 J-pipe delete adapter, billet aluminum, anodized black
• (1) Stainless steel exhaust gasket, fire-rated, marine-grade
• (1) Water-injection adapter (for cooling water reintroduction post-J-pipe)
• (6 ft) High-temperature silicone water hose, 3/4" ID
• (4) Stainless worm-gear hose clamps, #12
• (6) M10 × 35 mm SHCS — manifold mounting (high tensile, marine-grade)
• (6) M10 stainless flat washers
• (1) Hardware bag — spare gasket, spare clamps, water-injection check valve
• (1) High-temperature exhaust sealant tube, 4 oz
• (1) GT40 product registration card
• (1) This guide

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

Tools Required

• 10 mm / 13 mm / 17 mm sockets + ratchet, 3/8" drive
• T25 + T30 Torx drivers
• 5 mm + 6 mm + 8 mm hex (Allen) keys
• 3/8" drive torque wrench, 10–60 Nm range
• Long extension bars
• Hose-clamp pliers
• Marine-grade exhaust sealant applicator (small brush)
• Flashlight or headlamp
• Shop towels
• Marine-grade copper anti-seize compound

Safety

Read in full before starting.

1. Battery disconnected for the duration of the install.
2. Cold engine only. Factory J-pipe retains heat for over an hour after operation.
3. Eye protection mandatory when working around the exhaust manifold.
4. Hand protection. Marine exhaust has sharp flange edges.
5. No smoking / open flame.
6. Two-person lift recommended for the stainless rear exhaust outlet positioning.

If you are not comfortable with PWC exhaust system work, take the install to a certified marine technician.

Pre-Install Checklist

• [ ] Watercraft on stable trailer or stand
• [ ] Hull HIN year verified — 2016, 2017, 2018, or 2019 (NOT 2020+)
• [ ] Battery negative disconnected and isolated
• [ ] Engine bay clean and dry
• [ ] Factory J-pipe + waterbox routing photographed before disassembly
• [ ] Ribbon delete already installed if running Stage 2+ (GT40-SD-RDK-SD300)
• [ ] Marine-grade anti-seize ready
• [ ] 2 hours minimum for install + 2 hours sealant cure scheduled before first start

Step-by-Step Install

Step 1 — Access the Engine Bay and Identify the Factory Exhaust

Remove the seat. The 2016-2019 RXP-X hull configuration places the engine compartment access under the front of the seat assembly. On 2019 specifically, an additional inner panel must be lifted to reveal the J-pipe routing.

Disconnect the battery negative terminal.

Locate the factory J-pipe — curves rearward from the exhaust manifold around the engine block, into the waterbox, then to the through-hull exit.

Step 2 — Remove the Factory J-Pipe and Rear Exhaust

The 2016-2019 RXP-X 300 uses BRP's earlier-generation exhaust system. Note: this is functionally similar to the later RXT-X 300 but the J-pipe geometry differs slightly (tighter radius on the RXP-X hull).

1. Disconnect cooling water injection lines feeding the J-pipe (2 small hose connections, spring clamps)
2. Loosen the J-pipe-to-manifold V-band clamp (13 mm)
3. Loosen the J-pipe-to-waterbox V-band clamp (13 mm)
4. Lift the J-pipe out — heavy, ~7 lbs on this hull
5. Disconnect the waterbox inlet/outlet
6. Lift the waterbox out
7. Remove the through-hull rear exhaust outlet (this stays in the hull — only the internal pipe is being replaced)

Set all stock components aside. Do not discard if you may sell the craft in stock form later.

Step 3 — Inspect and Clean the Manifold Outlet Flange

1. Wipe the manifold outlet flange clean with shop towels
2. Inspect the gasket surface — must be flat, no carbon scoring
3. Light scuff with 220-grit sandpaper if any surface contamination
4. Final wipe with a clean solvent wipe
5. Allow 60 seconds for full solvent evaporation

Step 4 — Install the GT40 J-Pipe Delete Adapter

1. Apply marine anti-seize to all 6 M10 × 35 mm SHCS threads
2. Position the supplied stainless gasket on the manifold flange
3. Apply a thin even bead of high-temperature exhaust sealant around the gasket's outboard face
4. Position the GT40 J-pipe delete adapter against the gasket
5. Thread all 6 M10 SHCS through the adapter with flat washers — hand-tight only
6. Confirm the adapter is square to the manifold
7. Torque the 6 bolts to 42 Nm (31 ft-lb) in a star pattern across two passes
8. Wipe any sealant squeeze-out

Step 5 — Install the Stainless Rear Exhaust Outlet

1. Apply marine anti-seize to the stainless outlet's mounting flange threads
2. Position the outlet against the J-pipe delete adapter's exit flange
3. Thread the supplied V-band clamp around both flange edges
4. Snug the clamp finger-tight
5. Rotate the outlet to align with the through-hull exit point — the stainless outlet end must enter the through-hull fitting straight
6. 2016-2017 hull note: these years have a slightly tighter through-hull approach angle than 2018-2019. If the outlet doesn't seat cleanly, do not force it — contact GT40 support for a model-year-specific shim
7. Once aligned, torque the V-band clamp to 22 Nm (16 ft-lb) in two passes
8. Verify the outlet exits the hull cleanly — no contact with hull fiberglass

Step 6 — Reintroduce Cooling Water Injection

The J-pipe delete removes the factory cooling water reintroduction at the J-pipe top. Replacement injection sits in the GT40 adapter.

1. Locate the cooling water source on the engine block (3/8" NPT port near the rear of the head)
2. Locate the GT40 adapter's water injection port
3. Cut the supplied silicone water hose to length from source to injection point
4. Slide #12 clamps onto each hose end
5. Push the hose onto the source fitting, then the adapter water-injection port
6. Tighten both clamps to 3 Nm (27 in-lb) equivalent
7. Verify hose routing avoids contact with the hot exhaust adapter — minimum 25 mm clearance to any exhaust surface
8. Install the supplied check valve inline — prevents exhaust backflow if the engine ever runs without water

Step 7 — Allow Sealant Cure Time

Exhaust sealant requires a minimum of 2 hours cure time before engine start. Do not skip.

Overnight cure recommended for full strength.

Step 8 — Reassembly and First Start

After cure:

1. Walk the engine bay — every fastener, every clamp, every hose joint
2. Confirm no tools or hardware remaining
3. Reconnect the battery negative terminal — torque to 10 Nm (89 in-lb)
4. Replace the engine bay hatch, storage bin, seat
5. Connect the engine cooling flush hose
6. Start the engine on the trailer
7. Idle for 60 seconds — listen for any exhaust leak
8. Verify cooling water flow through the new injection point — observe steam from the rear exhaust outlet
9. Bring the engine to 3000 RPM briefly — confirm new exhaust note
10. Scan with BUDS or compatible OBD diagnostic — no new fault codes
11. After shutdown, visually inspect the J-pipe delete adapter for any sealant migration

If clean: install complete.

Post-Install

Break-In

First water test should run a conservative throttle profile for the first 5 minutes — gradual ramp to half throttle. Sealant cures fully under operating temperature on the first heat cycle. After 5 minutes at part throttle, full throttle pulls are safe.

The exhaust note will be louder than stock. The 2016-2019 RXP-X hull resonates around 4500-5000 RPM with this kit — some hull buzz at that range is normal hull acoustics, not a fault.

Tuning

This kit is mechanical-only at the stock 300HP calibration. No ECU tune required for fitment. Stage 2 / Stage 3 tunes will fully utilize the reduced backpressure for measurable gains.

For full Stage 3 systems on the 2016-2019 RXP-X, pair with:

• GT40-SD-INT-CF cold air intake
• GT40-SD-TUBE-230300-BOV charge tubing
• GT40-SD-OLC-300 open loop cooling (mandatory above 280 HP)
• Stage 3 calibration via Magic Module or equivalent

Service

• Inspect the J-pipe delete adapter every 25 run hours for any sealant weep
• Re-torque the 6 M10 SHCS at the first 10-hour service to 42 Nm
• Inspect the stainless outlet annually for any galvanic corrosion at the through-hull contact (stainless is corrosion-resistant but check for surface pitting in saltwater operation)
• Inspect the cooling water injection hose every 25 hours — replace if any cracking
• After 200 hours, plan a full exhaust sealant inspection

Troubleshooting

| Symptom | Likely Cause | Fix |

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

| Sharp ticking at manifold-to-adapter joint | Gasket failure | Stop, drain, replace gasket + sealant, reinstall |

| Stainless outlet doesn't seat in through-hull | 2016-2017 angle mismatch | Contact GT40 support for model-year shim |

| Exhaust gas smell in engine bay | J-pipe delete adapter leak | Retorque to 42 Nm, monitor, re-seal if persists |

| Steam in the engine bay after run | Cooling water injection hose failure | Inspect, replace hose, retorque clamps |

| Engine performance unchanged | No supporting tune | Pair with Stage 2 / Stage 3 calibration for measurable gain |

| Check Engine + P0420 | Not applicable on PWC | Sea-Doo has no catalyst; verify code is real |

| Loud resonance around 4500-5000 RPM | Normal hull acoustics | Not a fault — hull resonates at this RPM with the new exhaust |

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

Torque Reference Summary

| Fastener | Torque |

|---|---|

| J-pipe delete adapter to manifold M10 SHCS (all 6) | 42 Nm / 31 ft-lb |

| Stainless outlet V-band clamp | 22 Nm / 16 ft-lb |

| Cooling water injection #12 hose clamps | 3 Nm / 27 in-lb (snug, no hose-wall cut) |

| 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
• Damage from premature engine start before full sealant cure
• Damage from operation without proper cooling water flow through the new injection point
• Damage to stainless components from galvanic corrosion in saltwater without sacrificial anode protection
• Use on craft outside the listed fitment matrix (notably: any 2020+ RXP-X hull — that's a different kit)

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.