--- id: seadoo-gtx-di-2001 session-date: 2026-04-26 kind: equipment --- # Verified configuration | Field | Value | Source | |---|---|---| | Make/model | Sea-Doo GTX DI | Seat tag (photographed) | | Year | 2001 | EPA emission label, engine family `1BCXM.9514CD` (leading "1" = MY 2001) | | HIN | `ZZN39747A101` | Michigan boat registration (photographed 2026-04-26); cross-confirms image-processed read of plate | | Engine | 951cc 2-stroke twin, air-assisted DI | EPA label | | Engine family | `1BCXM.9514CD` | EPA label | | Power | 93 kW / ~125 hp | EPA label | | Spark plug | NGK ZFR4F-11, gap 0.043" / 1.1 mm | EPA label | | Idle spec | 1450 RPM ± 50 | EPA label | | Cooling | Open-loop seawater (no closed-loop coolant) | Engine architecture | | Lubrication | 2-stroke oil injection from separate tank | Engine architecture | | Hull total hours | ~120 | User-reported | | Hours since rebuild | ~25 | User-reported | | Watercraft Decal | 6052920 | MI registration | | Decal expiration | 31-Mar-2028 | MI registration | | Registered owner | Samuel Michael Foran, 4289 Bluebird Dr, Commerce Township MI 48382-4011, Oakland County | MI registration | --- # Symptoms / scope **End-of-last-season symptoms:** - 10–20% loss in both max RPM AND top speed compared to baseline 2 years prior at purchase - Maintenance light ON - Rough running **Critical context:** the engine was rebuilt approximately 2 years ago at the time of purchase. Only ~25 hours on the rebuild. ~120 hours total on the hull. The power deficit was developing pre-storage — winterization is incidental to the diagnosis, not the cause. **Combined RPM-and-speed deficit is diagnostic.** Pump slip would manifest as RPM rising while speed falls; both falling together points upstream of the impeller into the engine itself. Pump-slip family of causes (worn impeller, blown wear ring, cavitation) is ruled out by symptom pattern alone. **Currently:** winterized, awaiting pre-launch. Nothing physical done yet. No parts ordered. No diagnostic procedures executed. --- # Diagnoses / hypotheses considered See `diagnostic-logs/DHL-001-engine-family-identification.md` for the engine family resolution (4-TEC supercharged ABANDONED, 951 DI 2T CONVERGED). DHL-002 will open at next active session for the power-loss hypotheses with evidence as findings come in. **Current ranking (post-reframe, before scan/test):** | # | Hypothesis | Status | Notes | |---|---|---|---| | 1 | MPEM in protect/limp mode from stored fault (overheat / knock / low-oil / TPS) | Pending — highest priority | Single hypothesis cleanly explains both symptoms + maintenance light. Resolves with scan. Cheapest to verify. | | 2 | Crank seal leak (PTO or magneto side) | Pending | Classic 2-stroke power-loss mode. Common rebuild shortcut if seals reused. Indicator: plug color asymmetry between cylinders. | | 3 | Air compressor wear (DI-specific) | Pending | If reed valves not refreshed in rebuild, air rail pressure drops → mixture goes rich → power falls progressively. | | 4 | Cylinder glazing / rings not seated | Pending | Improper break-in by previous owner. Bluish smoke under load is the tell. | | 5 | RAVE valves carboned/sticking | Pending — low probability at 25 hrs | Possible if running rich. | | 6 | Exhaust restriction (water-logged tuned pipe / collapsed muffler) | Pending | Caps top end specifically. | | 7 | Pump slip (impeller wear / wear ring / cavitation) | Ruled out | Symptom pattern excludes — RPM and speed fell together, not divergent. | | 8 | 4-TEC supercharger failure | Ruled out | Wrong engine family. See DHL-001. | --- # Actions taken this session **Information gathering:** - HIN plate photographed and image-processed (`ZZN39747A` confirmed via plate; full HIN later verified from MI registration as `ZZN39747A101`) - EPA emission label photographed and decoded - Seat tag photographed and decoded - MI boat registration photographed (canonical HIN source, decal info, ownership) **Decisions made (not yet executed):** - Seat cover: Hydro-Turf 1997–2002 GTX direct-fit kit, cover only (foam being reused pending press-test verification on disassembly), 1/4" stainless monel staples. Pricing ~$200 per market check (corrected from earlier ~$100 estimate which was stale data). **Deliverables produced:** - `guides/seadoo-gtx-di-2001/seadoo-gtx-di-2001-service-guide-v0.1.html` — initial service guide rendered against canonical template, against METHODOLOGY.md v1.2 - `guides/seadoo-gtx-di-2001/diagnostic-logs/DHL-001-engine-family-identification.md` — retroactive DHL capturing 4-TEC supercharger wrong turn for format validation **Nothing physical done.** No parts ordered. No diagnostic procedures executed. No service performed. The GTX DI is still on the trailer in winterized state. --- # Outstanding decisions / next steps **Diagnostic procedure (in order, gated on cheapest-first):** 1. DTC scan — try free cluster button combos at key-on first; if no result, $50–100 independent shop scan or $150–200 used CanDoo Pro 2. Plug pull and color comparison between cylinders (asymmetry = crank seal indicator) 3. Compression test, both cylinders (cold engine, plugs out, DESS disconnected, throttle WOT) 4. Air compressor audible check during cranking (tick-tick rhythm, finger-test pressure pulse at air rail Schrader) 5. Oil pump bleed verification (must be done before any start if tank ran dry) **Information needed:** - Rebuild documentation if available — receipts, parts list, identity of rebuilder. Determines whether to weight crank seal vs. air compressor reed vs. cylinder glaze hypotheses. - Service manual access for OEM verification of items currently flagged `// UNVERIFIED` in v0.1 guide: - Spark plug torque (NGK ZFR4F-11 size class, ~16 ft-lb recalled but unverified) - Compression spec OEM minimum (115–135 psi field range recalled) - RAVE valve cover bolt torque - Air rail pressure spec - External fuel filter, RAVE bellows, air compressor kit, crank seal kit part numbers **Decisions pending Sam:** - Scan tool path (free button combos vs. $50–100 shop vs. $150–300 own purchase) - Rebuild documentation hunt — has direct bearing on hypothesis weighting - Whether to execute Phase 1 service items in parallel with diagnostic, or strictly sequential **Path to v0.2:** - Resolve all `// UNVERIFIED` items via service manual access - Open DHL-002 with evidence-tracked power-loss hypotheses as physical findings come in - Update guide with scan results, plug colors, compression numbers - Lock part numbers for Tier 2/3 shopping list --- # Confidence assessment **High confidence:** - Equipment identification (HIN canonically verified via MI registration, EPA label intact) - Diagnostic hypothesis ranking (symptom pattern rules in/out specific failure-mode families cleanly) - Seat cover compatibility window (1997–2002 GTX shared seat shape is well-documented) **Medium confidence:** - Rebuild quality concern is real but unquantified — 10–20% loss at 25 hours on a fresh rebuild is not normal wear, but root cause within the rebuild is undetermined. Could be any of #2/3/4 from the hypothesis ranking. **Low confidence / flagged for v0.2:** - All `// UNVERIFIED` torque values, compression specs, and part numbers in the v0.1 guide. v0.1 was a format-validation milestone, not an OEM-verification milestone. Do not torque to v0.1 numbers without service manual cross-check. - Seat cover pricing — market check at time of order required; pricing rots faster than fitment. **Substrate state at session end:** - Canonical METHODOLOGY.md v1.2 verified live (cache-bust required to bypass session web_fetch cache; standard fix is `?v=N` query string per SESSION-PRELUDE.md v1.0.1 Class 4 patch landing separately) - v0.1 guide rendered against canonical v1.2 (Principle 8 reflected in process; render content unaffected by v1.1→v1.2 delta since the delta is governance not engine specs) **Next-session boot:** fetch this handoff block and `index/equipment/seadoo-gtx-di-2001.md` first, then v0.1 guide, then DHL-001. Restore full diagnostic context. Open DHL-002 for power-loss hypotheses.