Legacy 215HP Rear Exhaust Kit — Install Guide

GT40 Marine | SKU GT40-SD-EXH-215 | Stainless Rear Exhaust + OPAS Block-Off | Rev 1.0 — 2026-05-24

Fitment

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

| Sea-Doo | RXP 215 | 2004–2009 | 1503 4-TEC 215 |

| Sea-Doo | RXT 215 | 2005–2009 | 1503 4-TEC 215 |

| Sea-Doo | GTX Limited 215 | 2008–2010 | 1503 4-TEC 215 |

| Sea-Doo | GTX 215 | 2008–2010 | 1503 4-TEC 215 |

Not for: 230 / 260 / 300 / 325 HP. Not for 1630 ACE platform. OPAS-equipped craft note: craft with the OPAS (Off-Power Assisted Steering) system on the legacy 1503 4-TEC platform may require the supplied OPAS block-off plate to seal the cooling-water bypass that the OPAS system used. Verify your craft's OPAS configuration in Pre-Install Step 0.

In the Box

(1) GT40 stainless steel rear exhaust outlet, hand-formed, mirror-polished
(1) Exhaust adapter for legacy 1503 4-TEC manifold geometry
(1) Stainless steel exhaust gasket, fire-rated, marine-grade
(1) OPAS block-off plate (optional use per fitment) + gasket
(1) Water-injection adapter
(4 ft) High-temperature silicone water hose, 3/4" ID
(4) Stainless worm-gear hose clamps, #12
(6) M10 × 30 mm SHCS — manifold mounting
(6) M10 stainless flat washers
(4) M6 × 20 mm SHCS — OPAS block-off mounting (if used)
(4) M6 stainless flat washers
(1) High-temperature exhaust sealant tube, 4 oz
(1) Hardware bag — spare gasket, spare clamps
(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, 5–60 Nm range
Long extension bars (legacy hull access is tight)
Hose-clamp pliers
Marine-grade exhaust sealant applicator
Flashlight or headlamp
Shop towels
Marine-grade copper anti-seize compound

Safety

Read in full before starting.

Battery disconnected for the duration of the install.
Cold engine only. The 1503 4-TEC retains heat for over an hour after operation.
Eye protection mandatory around the exhaust manifold.
Hand protection. Legacy marine exhausts often have heavier carbon buildup than newer platforms — wear nitrile gloves under leather work gloves.
No smoking / open flame.
Older craft caution. 2004-2010 hulls may have undocumented modifications from previous owners — proceed deliberately and photograph everything before disassembly.

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
[ ] Step 0 — OPAS verification: Inspect the rear of the engine bay for the OPAS hydraulic actuator (a small cylinder with a steel rod connected to the rear of the hull). If present, you will use the supplied OPAS block-off plate. If absent (some craft had OPAS removed by previous owners), skip the OPAS block-off step.
[ ] Hull HIN confirmed within fitment year range
[ ] Battery negative disconnected and isolated
[ ] Engine bay clean and dry (legacy craft may have accumulated debris — vacuum before opening any joints)
[ ] Factory J-pipe + waterbox routing photographed
[ ] Marine-grade anti-seize ready
[ ] 3 hours minimum for install + 2 hours sealant cure scheduled before first start (legacy craft are typically slower to disassemble due to corrosion on stock fasteners)

Step-by-Step Install

Step 1 — Access the Engine Bay

Remove the seat and engine bay top hatch. On 2004-2007 hulls, an additional inner panel may need removal. On 2008-2010 hulls, the access is more open.

Disconnect the battery negative terminal.

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

The legacy 1503 4-TEC supercharged exhaust system consists of:

A J-pipe running from the manifold around the engine
A waterbox (often larger/heavier than later-generation waterboxes)
A rear-outlet pipe to the through-hull discharge

Removal sequence:

Disconnect cooling water injection lines feeding the J-pipe — typically 2-3 small hose connections on legacy craft, more than newer platforms
Loosen the J-pipe-to-manifold V-band clamp (13 mm) — these are often corroded on legacy craft; apply penetrating oil 5 minutes before attempting
Loosen the J-pipe-to-waterbox V-band clamp (13 mm)
Lift the J-pipe out — heavy, ~9 lbs on legacy craft
Disconnect the waterbox inlet/outlet
Lift the waterbox out — bulky, plan a clear path; legacy waterboxes are larger than current ones
If OPAS-equipped: locate the OPAS hydraulic actuator and disconnect its lines from the cooling system. Inspect the cooling-water bypass port that fed the OPAS system — this is the port that will receive the block-off plate

Set all stock components aside. Do not discard.

Step 3 — Inspect and Clean the Manifold Outlet Flange

Wipe the manifold outlet flange clean with shop towels
Inspect for warping (legacy craft sometimes have heat-warped manifold flanges from years of operation)
If warping is severe (>0.5 mm out of flat), stop and contact GT40 support — the kit cannot seal against a warped factory flange
Light scuff with 220-grit sandpaper to clean
Final wipe with a clean solvent wipe
Allow 60 seconds for full solvent evaporation

Step 4 — Install the OPAS Block-Off Plate (if applicable)

Skip this step if the craft is not OPAS-equipped.

Apply marine-grade thread sealant to the supplied OPAS block-off plate gasket O-ring
Position the block-off plate over the OPAS bypass port
Thread the 4 supplied M6 × 20 mm SHCS with flat washers
Snug evenly in a cross pattern, then torque to 8 Nm (71 in-lb)
Visual check — block-off plate sits flat with no daylight at the O-ring perimeter

Step 5 — Install the GT40 Exhaust Adapter

The exhaust adapter mates the legacy 1503 4-TEC manifold to the modern GT40 outlet geometry.

Apply marine anti-seize to all 6 M10 × 30 mm SHCS threads
Position the supplied stainless gasket on the manifold flange
Apply a thin even bead of high-temperature exhaust sealant around the gasket's outboard face
Position the GT40 exhaust adapter against the gasket
Thread all 6 M10 SHCS through the adapter with flat washers — hand-tight only
Confirm the adapter is square to the manifold
Torque the 6 bolts to 38 Nm (28 ft-lb) in a star pattern across two passes — first pass at 20 Nm, second pass at 38 Nm. Note: torque is lower than newer platforms (42 Nm) because legacy manifold flange material is more susceptible to thread pull-out
Wipe any sealant squeeze-out

Step 6 — Install the Stainless Rear Exhaust Outlet

Apply marine anti-seize to the stainless outlet's mounting flange threads
Position the outlet against the GT40 adapter's exit flange
Thread the supplied V-band clamp around both flange edges
Snug the clamp finger-tight
Rotate the outlet to align with the through-hull exit point
2004-2007 hull note: these years have a wider through-hull approach angle than 2008-2010. The outlet should seat with no force; if it doesn't, contact GT40 for a model-year shim
Once aligned, torque the V-band clamp to 22 Nm (16 ft-lb) in two passes
Verify the outlet exits the hull cleanly

Step 7 — Reintroduce Cooling Water Injection

Locate the cooling water source on the engine block — on legacy 1503 4-TEC, this is typically a 3/8" NPT port near the rear cylinder head
Locate the GT40 adapter's water injection port
Cut the supplied silicone water hose to length
Slide #12 clamps onto each hose end
Push the hose onto the source fitting, then the adapter water-injection port
Tighten both clamps to 3 Nm (27 in-lb) equivalent
Verify hose routing avoids contact with the hot adapter — minimum 25 mm clearance

Step 8 — Allow Sealant Cure Time

Exhaust sealant requires a minimum of 2 hours cure time before engine start.

For legacy craft, overnight cure is strongly recommended — the older manifold material benefits from longer cure time.

Step 9 — Reassembly and First Start

After cure:

Walk the engine bay — every fastener, every clamp, every hose joint
Confirm no tools or hardware remaining
Reconnect the battery negative terminal — torque to 10 Nm (89 in-lb)
Replace the engine bay hatch and seat
Connect the engine cooling flush hose
Start the engine on the trailer
Idle for 60 seconds — listen for any exhaust leak
Verify cooling water flow through the new injection point
Bring the engine to 3000 RPM briefly — confirm new exhaust note
Scan with BUDS or equivalent legacy diagnostic — no new fault codes
After shutdown, visually inspect the 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. Legacy 1503 4-TEC engines are typically older with higher cumulative wear — be more conservative on the first heat cycle than you would be on a new craft.

The exhaust note will be louder than stock. The 1503 4-TEC's factory exhaust attenuated significantly more than newer platforms — expect a pronounced character change.

Tuning

This kit is mechanical-only at the stock 215HP / 255HP calibration. No ECU tune required for fitment.

Note: legacy 1503 4-TEC tuning is more limited than the 1630 ACE platform. Expect 5-8 HP gain from this exhaust on a stock craft, 15-25 HP gain with a matched legacy-platform tune + supporting modifications.

Service

Inspect the GT40 adapter every 25 run hours for any sealant weep
Re-torque the 6 M10 SHCS at the first 10-hour service to 38 Nm
Inspect the stainless outlet annually for galvanic corrosion
Inspect the cooling water injection hose every 25 hours
Legacy craft typically need exhaust sealant refresh every 100 hours due to the older manifold material flexibility
Inspect the OPAS block-off plate (if installed) annually for any seepage

Troubleshooting

| Symptom | Likely Cause | Fix |

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

| Sharp ticking at manifold-to-adapter joint | Gasket failure / legacy manifold warp | Stop, inspect manifold flatness, replace gasket + sealant if flatness is OK |

| Stainless outlet doesn't seat in through-hull | 2004-2007 angle mismatch | Contact GT40 support for model-year shim |

| Exhaust gas smell in engine bay | Adapter leak | Retorque to 38 Nm, monitor, re-seal if persists |

| Coolant leak from OPAS block-off plate | O-ring not seated | Drain, replace O-ring, retorque to 8 Nm |

| 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 legacy-platform Stage 2/3 tune for measurable gain |

| Significant exhaust manifold seepage at gasket | Manifold flange warping | Stop operation, contact GT40 for inspection — may require manifold rework |

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

Torque Reference Summary

| Fastener | Torque |

|---|---|

| GT40 adapter to manifold M10 SHCS (all 6) | 38 Nm / 28 ft-lb |

| OPAS block-off plate M6 SHCS (all 4, if used) | 8 Nm / 71 in-lb |

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

| Cooling water injection #12 hose clamps | 3 Nm / 27 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. Note: torque on legacy manifold M10 SHCS is intentionally lower than newer platforms due to the older manifold material's flange properties.

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
Damage caused by pre-existing manifold flange warping (this is a legacy-craft inspection responsibility per Step 3)
Damage from incorrect OPAS configuration handling
Use on craft outside the listed fitment matrix

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, your hull serial number, and the model year in any support correspondence (the model year matters more than any other variable on this kit)

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