Shorty Water Box + Free-Flow Exhaust — Install Guide

GT40 Marine | SKU GT40-SD-WB-1630ACE | Universal 1630 ACE Shorty Water Box | Rev 1.1 — 2026-05-24

---

Fitment — All 2020+ Sea-Doo with the 1630 ACE Engine

This waterbox fits the entire 1630 ACE engine family across 2020-2026 model years, regardless of HP tier (130 / 170 / 230 / 300 / 325). The waterbox sits downstream of the exhaust manifold — fitment is determined by the engine block + hull mounting geometry shared across the whole 1630 ACE platform, NOT by HP rating.

130 HP

170 HP

230 HP

300 HP

325 HP

Not for: 1503 4-TEC engines (legacy 2002-2018), Spark (900 ACE), Switch platform (different exhaust architecture), pre-2020 craft of any kind. Confirm engine block stamping reads "1630 ACE" before install.

---

Before You Start — Decision Tree

This is a Stage 2+ component — useful when paired with supporting modifications. Answer these before opening packaging:

---

In the Box

• (1) GT40 Shorty Water Box, aluminum, ceramic-coated interior
• (1) Inlet adapter ring (mates to factory J-pipe or GT40 J-pipe delete)
• (1) Outlet adapter ring (mates to rear exhaust outlet)
• (2) Stainless V-band clamps, 3" ID
• (2) High-temperature exhaust gaskets, fire-rated, marine-grade
• (4) M10 × 30 mm SHCS — bracket mounting
• (4) M10 stainless flat washers
• (1) GT40 mounting bracket (replaces factory waterbox mounting straps)
• (1) High-temperature exhaust sealant tube, 4 oz
• (1) Hardware bag — spare V-band, spare gasket
• (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 (engine bay access varies by hull — RXP-X/RXT-X tighter than GTX)
• 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 waterbox retains heat for over an hour after operation.
3. Eye protection mandatory when working around the exhaust system.
4. Hand protection. Sharp flange edges on marine exhaust components.
5. No smoking / open flame.
6. Two-person lift recommended for the shorty box positioning, particularly on 300/325 HP craft where the factory waterbox is heaviest.

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
• [ ] Engine block stamping confirmed as "1630 ACE"
• [ ] Hull HIN year confirmed as 2020 or later
• [ ] Battery negative disconnected and isolated
• [ ] Engine bay clean and dry
• [ ] Factory waterbox routing photographed before disassembly
• [ ] Ribbon Delete Kit installed if on 300/325 HP application (recommended for 130/170/230 HP, optional)
• [ ] 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

Remove the seat. On RXP-X / RXT-X, also lift the rear storage bin to expose the engine bay top hatch. On GTX / GTR / Wake Pro / FishPro / Explorer Pro hulls, the access may be via a top hatch or front service hatch — refer to the BRP service manual for your specific hull.

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

Step 2 — Remove the Factory Waterbox

The factory waterbox varies in size across HP tiers (larger on 300/325HP than on 130/170HP) but uses the same mounting geometry and V-band interface across the family.

1. Disconnect cooling water injection lines feeding the waterbox (2 small hose connections, spring clamps)
2. Loosen the inlet V-band clamp (where J-pipe meets waterbox)
3. Loosen the outlet V-band clamp (where waterbox meets rear-exhaust pipe)
4. Disconnect factory mounting straps (2 straps, 13 mm fasteners)
5. Lift the waterbox out — weight varies: ~7 lbs on 130/170 HP, ~9 lbs on 230 HP, ~10 lbs on 300/325 HP. Plan a clear path on the larger units.
6. Inspect the inlet and outlet V-band groove for any damage — must be undamaged for the new GT40 unit to seal

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

Step 3 — Install the GT40 Mounting Bracket

The Shorty Water Box uses a different mounting geometry than the factory unit. The supplied GT40 bracket replaces the factory mounting straps.

1. Position the GT40 bracket against the engine bay mounting bosses (the 1630 ACE platform has pre-drilled mounting bosses at the bracket location — they're visible as 8 mm tapped holes on the inboard engine bay sidewall)
2. Thread the 4 M10 × 30 mm SHCS through the bracket with flat washers
3. Snug all 4 evenly, then torque to 35 Nm (26 ft-lb) in a cross pattern across two passes
4. Verify the bracket sits plumb and the Shorty Water Box will mate squarely with the inlet and outlet exhaust pipes

Step 4 — Pre-Fit the Shorty Water Box

Before applying any sealant, dry-fit the box to verify alignment:

1. Position the supplied inlet adapter ring on the J-pipe outlet (or GT40 J-pipe delete adapter exit)
2. Position the supplied outlet adapter ring on the rear exhaust pipe inlet
3. Position the GT40 Shorty Water Box between the two adapter rings
4. Verify the box sits cleanly on the GT40 mounting bracket with no side load
5. Verify the inlet/outlet V-band grooves align perfectly with the adapter rings — no angular offset
6. If alignment is off: re-check Step 3 bracket position and adjust before proceeding

Step 5 — Install with Sealant

1. Apply marine anti-seize to all V-band clamp bolt threads
2. Position the inlet exhaust gasket between the adapter ring and the J-pipe outlet
3. Apply a thin bead of high-temperature exhaust sealant around the inlet gasket's outboard face
4. Position the Shorty Water Box, aligning the inlet V-band groove with the adapter ring
5. Slide the supplied V-band clamp around the joint
6. Snug the inlet V-band finger-tight
7. Repeat for the outlet (gasket → sealant → V-band on the outlet adapter ring)
8. Once both V-bands are positioned and the box is properly aligned, torque both V-band clamps to 22 Nm (16 ft-lb) in two passes
9. Wipe any sealant squeeze-out

Step 6 — Reconnect Cooling Water Injection

1. Locate the two cooling water injection ports on the new GT40 Shorty Water Box (top face)
2. Reconnect the two factory injection hoses, ensuring spring clamps are properly seated
3. Verify hose routing avoids contact with the hot box body — minimum 25 mm clearance

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 V-band, 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 (sharp ticking, sustained whistling)
8. Verify cooling water flow through the new injection points — observe steam from the rear exhaust outlet
9. Bring the engine to 3000 RPM briefly — confirm new free-flow exhaust note (noticeably louder on lower-HP, dramatic on 300/325 HP)
10. Scan with BUDS or compatible OBD diagnostic — no new fault codes
11. After shutdown, visually inspect both V-band joints 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 final cure happens during this period under full operating temperature.

Exhaust note change varies by HP tier:

• 130/170 HP: subtle increase, more crisp than dramatic
• 230 HP: noticeable increase above 4000 RPM
• 300/325 HP: substantially louder than stock above 5000 RPM, dramatic free-flow character

Some hulls resonate at certain RPM — this is hull acoustics, not a fault.

Tuning

This kit is mechanical-only across the entire 1630 ACE family. No ECU tune required for fitment.

Gain by HP tier (mechanical-only, no tune):

• 130/170 HP: 3-5 HP
• 230 HP: 4-6 HP
• 300/325 HP: 8-12 HP

For full Stage 2 / Stage 3 builds on 300/325 HP applications, pair with:

• GT40-SD-RDK-SD300 Ribbon Delete (required)
• GT40-SD-EXH-ST3 Stage 3 Exhaust + J-pipe Delete (for full exhaust path)
• GT40-SD-INT-CF or GT40-SD-INT-325 Cold Air Intake
• GT40-SD-TUBE-230300-BOV or GT40-SD-TUBE-325-BOV charge tubing
• Stage 2 or Stage 3 calibration via Magic Module or equivalent

Service

• Inspect both V-band joints every 25 run hours for any sealant weep
• Re-torque both V-bands at the first 10-hour service to 22 Nm
• Inspect the GT40 mounting bracket every 50 hours for fastener security
• After 200 hours, plan a full exhaust sealant inspection
• Inspect the ceramic-coated interior annually (visible via the inlet/outlet opening) — recoat if visible degradation

---

Troubleshooting

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

---

Torque Reference Summary

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 injection points
• Damage from operation outside the 1630 ACE engine family
• Use on craft outside the listed fitment matrix (notably: any 1503 4-TEC, Spark, or pre-2020 craft)

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, the model year, and the HP rating 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.

Replaces the earlier GT40-SD-WB-325 draft — same physical product, broader fitment confirmed 2026-05-24 to cover entire 1630 ACE engine family (130-325 HP, 2020-2026 model years).