A complete course for trained marine diesel techs: clean the room, remove & reinstall, measure the running gear, fit, install & align, common-rail handling, commission — plus the four mandatory ABYC modules. Lessons, procedures, specs and checks.
Before you start
For trained marine diesel technicians. Each chapter is a full lesson — objectives, the why, step-by-step procedure and specs — ending with a check. The four ABYC modules and the final exam are hard-pass gates: your ESI Technician / Installer certificate stays locked until all are passed. The original Yanmar slide decks are a separate supplement, not part of this course.
Reference Doc A, Reference Doc B and the Shaft Go/No-Go tool launch from the relevant chapters.
P-4, P-1, H-33 and E-11 are taught here and must each be passed.
Pass the four ABYC gates + final exam to unlock the certificate.
Chapter 1
The engine is out — this is the one clean shot you get for years.
An empty engine bay is the only time you can properly clean, inspect and paint the space. Do it before the new engine drops in — afterwards you'll never have this access again. A clean, sealed bilge isn't cosmetic: it's a working tool. A fresh leak shows up instantly against a bright epoxy floor, fasteners don't sit in old oil, and it's exactly what a surveyor and the customer expect from ESI.
With everything exposed, check the items you can't reach later: hoses and clamps, seacocks and bonding, stringers and engine-bed condition, and the shaft log. Flag anything for the estimate now.
Chapter 2
Getting the old engine out without wrecking the boat — and the new one in clean.
A 4JH-class engine is roughly 220–230 kg dry, plus the marine gear. It does not simply lift out — the path, the rigging and the order of operations are the job. Plan the lift before you touch a bolt.
Decide how it comes out: yard crane, travel-lift, a mast used as a derrick, or an A-frame and chain hoist — sometimes with the boat still in the water. Identify the route (companionway, deck hatch, removed joinery) and protect the interior. Confirm rated lifting points and slings.
Set the engine onto a fresh set of mounts (old mounts are oil-soaked and collapsed — never reuse). Rough-position it on the beds, then move to alignment in Chapter 5. Before the lift, confirm everything sales handed over is on hand: gearbox, mounts, coupler, GLIDE seal & cutless, prop work.
Chapter 3
Spec the shaft, seal, cutless and gear before you commit a single part.
Most repower call-backs are running-gear problems, not engine problems. Measure everything once, properly, and the rest of the job follows. Use the field tools — they're attached below and also live standalone.
Straightness is judged against the ABYC P-6-2021 / Aqualoy straightness table, which scales with length (e.g. ~5 thou over 3 ft, ~12.5 thou over 8 ft on the industry column). Because the GLIDE seal is a lip seal, the shaft surface at the seal band must be smooth — a score or groove there leaks. Pitting or crevice corrosion is an automatic reject: crevices seed cracks that propagate and fail under the higher torque of the new engine. Don't eyeball it — run the tool.
The GLIDE double-lip dripless seal is chosen between GMS and GMSS by the shaft-log-to-back-of-coupler length, then sized by shaft diameter × stern-tube OD. It must be fitted with the supplied install tool to keep the 4-year warranty, and the kit ships with a spare seal.
GLIDE cutless bearings follow ID × OD × length with length ≈ 4× shaft diameter (1″×1¼×4, 2″×2¾×8…). Set bearing-to-shaft clearance per the Navy/BuShips range for the shaft size (e.g. ¾–1⅜″ = .003–.008″); plan replacement at ~1 mm play, ~2 mm max, equal all round, flutes clear.
Chapter 4
Prove it fits — envelope, clearances and access — before the lift.
Footprints don't carry across generations — the 4JH differs from older 4JH/4JH2/4JH3, and competitor swaps differ more. Never promise a drop-in from the badge.
Measure bay length, width and height; bed spacing and height; and the removal/installation opening. Compare against the chosen 4JH-CR footprint, remembering the gearbox or saildrive adds length.
Leave room on all sides for service, thermal expansion and vibration on the soft mounts. Check overhead for the air filter and lifting eye, and confirm exhaust and intake can route cleanly.
Confirm you can reach oil fill and dipstick, fuel and oil filters, the belt, the raw-water pump and the seacock without dismantling joinery. If the envelope, clearances or access are tight or ambiguous, escalate to a site visit before the estimate is committed.
Chapter 5
Set it, align it, and connect every system to standard.
Prep and, if needed, shim or re-fair the engine beds so the mounts sit square and at the right height. Use the correct soft mounts; rough-set the engine close to its final line.
Align the shaft coupling to the gearbox output. The faces must be parallel within 0.004″ (0.10 mm), equal at four points around the flange, measured with the coupling bolts loose and the boat in the water (the hull changes shape on the hard). Don't force the shaft to the engine — move the engine on its mounts.
Build the wet exhaust so the riser/gooseneck crests well above the waterline and add a siphon break if the manifold can sit below the waterline at any heel. This is the single most common way a new engine is destroyed — water reversion (hydrolock). It's covered as a graded module later; build it right here.
Chapter 6
The Bosch CRS2-16 rules that keep the fuel system — and you — safe.
The 4JH-CR runs a Bosch CRS2-16 common rail at up to 1600 bar, with pilot/pre/main injection controlled by the ECU. At that pressure a leak can inject fuel through skin, and microscopic dirt ruins injectors — so cleanliness and the handling rules are not optional.
The rail is supplied as an assembly (non-repairable). After fitting, reset the PLV (Pressure Limiting Valve) historical data with SA-D.
Know the fail-safe responses too: a throttle-sensor fault drops to a fixed idle; an injector open/short stops that injector and limits speed/torque; a supply-pump fault limits speed. Diagnose them with SA-D rather than chasing symptoms.
Chapter 7
Hand it over running right — and prove the prop is correct.
Oil and coolant levels; fuel on and bled; belt tension; every clamp and fastener; mounts secure; seacock open. Belt deflection 8–9 mm at 100 N; valve clearance (if checked) 0.15–0.25 mm; low idle 800 min⁻¹; fuses present (alternator 200 A, starter 50 A, ECU 20 A).
Start and immediately confirm oil pressure, charging, coolant temperature, and cooling water at the exhaust outlet. Watch for fuel, oil and coolant leaks. Read DTCs on the panel / SA-D.
Run the break-in load schedule and do the first oil change up front (an ESI standard). Register the engine within 30 days. Hand over a checked, running boat and set the service reminders.
Chapter 8 · ABYC graded module
Mandatory graded module — the engine installation standard.
P-4 governs how an inboard engine and transmission are constructed and installed. For a repower it's your checklist that the engine is mounted, guarded, accessible and ventilated safely.
Exposed belt and chain drives and rotating parts must be guarded so they can't catch a hand or clothing in normal operation. An engine box that encloses the unit satisfies this.
Routine-maintenance points — oil fill, dipstick, coolant fill — must be reachable for normal maintenance without tools. If a repower buries the dipstick behind a panel, that's a fail; relocate or reroute.
A diesel engine space is ventilated per ABYC H-32-2023 (diesel) — not H-2, which is for gasoline. Mounting, coupling and shaft alignment must meet the standard (see Chapter 5).
Chapter 9 · ABYC graded module
Mandatory graded module — the standard that stops hydrolock.
P-1 covers exhaust-system installation. Get it wrong and seawater siphons back through the exhaust and hydrolocks the engine — a catastrophic, warranty-voiding failure that can happen the first time the boat sits in a following sea or decelerates hard.
Keep the exhaust outlet well above the waterline at all attitudes. The riser / gooseneck loop must crest high enough that water can't run back down into the engine.
If the exhaust manifold can sit below the waterline at any angle of heel, fit a siphon break, located so it stays above the waterline at all heel angles. It vents the loop and breaks any siphon.
Chapter 10 · ABYC graded module
Mandatory graded module — the diesel fuel standard.
H-33 covers the permanently installed diesel fuel system from the fill to the engine. On a repower you'll touch hoses, clamps and sometimes a gas-to-diesel tank conversion — all of it must meet this standard.
Every metallic fill and tank component in contact with fuel must be grounded to less than 1 ohm to the boat's ground, to dissipate static.
Flexible hose without permanently attached fittings is secured with corrosion-resistant metallic clamps — spring-tension-only clamps are not allowed. Use fire-resistant FKM hose to ISO 7840.
Fill lines run self-draining and as directly as practicable to the tank; vents carry a flame arrester and trap no liquid.
Chapter 11 · ABYC graded module
Mandatory graded module — the marine wiring standard.
E-11 governs AC and DC systems on boats. On a 4JH-CR repower it covers the engine harness, panel wiring, the alternator/regulator and battery isolation.
Every ungrounded conductor gets overcurrent protection within 7 inches of its connection to the power source — extendable to about 40 inches if the conductor is sheathed or run in conduit.
Conductors are generally 16 AWG minimum and stranded (never solid). Size for both ampacity and voltage drop over the run.
Wire in the engine space must be oil-resistant and rated to 105 °C for the heat. This is where a lot of repowers cut corners — use the right wire.
Chapter 12
How we work is part of the work. This applies to every job.
Skill gets the install right; discipline gets it done profitably and hands the customer a boat that's better than we found it. These habits run through every ESI field job.
Before you walk to the boat, plan the job and gather the tools, parts and equipment you'll need. Think it through end to end and stage it. A planned job is a fast job; a forgotten tool is a trip you didn't have to make.
Use a cart for each job. Stage your tools, parts and consumables on it so everything travels with you to the boat and stays in one place — not scattered, and not back in the shop.
Every trip back to the shop is unbillable time the customer doesn't pay for and the job eats. Walking costs money. Keep your tools organized and within reach so you're working, not searching or fetching.
Count the extra trips you make to the shop and record those numbers. Trips per job, tracked over time, show where pre-planning is slipping and where we can tighten up. Honest numbers, every job.
ESI runs on Kaizen — continuous improvement. Small better-ways found on the boat, captured every day, compound into a faster, sharper shop.
Field reference
Field-tested: the symptom, the usual cause, and the fix. Always diagnose before you replace parts.
| Symptom | Likely cause | Fix |
|---|---|---|
| Engine cranks but won’t start | Air in the fuel, closed fuel valve, dead lift pump, or kill-switch/ground | Bleed the fuel system, open the supply, confirm lift-pump prime and the kill-switch ground |
| Excessive vibration under way | Misalignment, tired mounts, wrong prop pitch, or a bent shaft | Re-align to 0.001–0.002″/in, fit new mounts, verify shaft runout and prop |
| Overheats on the sea trial | Closed raw-water seacock, bad impeller, airlock, or blocked strainer | Open the seacock, replace the impeller, bleed, clean the strainer and check the HX |
| Won’t reach rated WOT rpm | Over-pitched prop or a fouled bottom | Re-pitch the prop to hit WOT spec; clean the bottom and running gear |
| Smoke — black, white or blue | Air-restriction/over-fuel (black), coolant or air in fuel (white), oil (blue) | Check air intake & fuel, bleed, pressure-test the HX, look for oil carry-over |
| Low oil pressure alarm | Wrong oil grade, a faulty sender, or a genuine restriction | Confirm oil spec and level, test/replace the sender, stop and investigate if real |
| Exhaust or CO smell in the cabin | Loose clamps, cracked wet-exhaust hose, or a failed riser | Double-clamp with T-bolt clamps, replace the hose, confirm the CO alarm |
| Panel fault code / DTC | Sensor, connector or harness fault | Read the code and check the named sensor and its connector before replacing parts |
Final certification
A short check ran at the end of each chapter. Pass this final at 80% to unlock your certificate.
Runout allowance read live from the ABYC P-6-2021 / Aqualoy straightness table by length & basis. Corrosion / pitting = automatic reject.
Record: stern tube (bore/OD, length); shaft diameter (vernier, several points) and length to the back of the coupler (selects GLIDE GMS vs GMSS); coupler type/bolt pattern; cutless ID×OD×length.
| Check | Standard / rule |
|---|---|
| Shaft straightness | ABYC P-6-2021 / Aqualoy table by length (run the Shaft Go/No-Go tool) |
| Surface | GLIDE lip seal needs a smooth shaft; scored/pitted → replace |
| Cutless | ID×OD×length; length ≈ 4× shaft dia; ~1 mm play = plan replace, ~2 mm max |
| GLIDE seal | GMS vs GMSS by length to coupler; fit with the supplied tool (warranty) |
Footprints differ by generation — measure, don't assume. Record the bay envelope, side clearances and service access; compare to the 4JH-CR footprint (gearbox/saildrive adds length).
| Model | Aspiration | Approx width | Approx ht f/centre | Dry wt |
|---|---|---|---|---|
| 4JH45/57-CR | NA | 588 mm | 459 mm | 220 kg |
| 4JH80/110-CR | Turbo | 613 mm | 473 mm | 229 kg |
Approximate, OCR-derived — verify against current Yanmar outline drawings.