Akasaka Engine
Spare Parts Supplier
Akasaka Diesels low-speed four-stroke main engines · A28 to A45 · AX and AT · K, E, AH and U · UEC two-strokes built under licence
Akasaka engines a spare parts RFQ can reference
Akasaka Diesels Limited is an independent Japanese main-engine builder, listed in Tokyo, with its two plants, Toyoda and Nakaminato, in Yaizu, Shizuoka. The business began in 1910 repairing hot-bulb engines in Yaizu, built its first diesel in 1933 and was incorporated in 1934 as Akasaka Iron Works, which is still its Japanese company name. It runs two engine lines under one name, both built in Yaizu: its own four-stroke engines, developed in-house since 1933, and two-stroke UE engines built under a licence first granted by Mitsubishi Heavy Industries in 1960 and now held from Japan Engine Corporation (J-ENG). Cumulative output passed 10,000 engines in 2013. The maker lists Types A, AX and AT for cargo ships and tankers, Types K, E and AH for fishing vessels, Type U for ferries and government vessels, and its UE two-strokes for cargo ships and chemical tankers.
A28, A31, A34, A37, A38, A41 and A45
The long-stroke trunk-piston line behind most Akasaka requests, running from the smallest A frames up to the A45, built as a rule as an in-line six and run on heavy fuel. The frame number rises with the bore and the rated speed falls as it does. The practical point is the rating: the maker lists its later AT33 and AT33L as separate models with different output and speed on the same frame size, and two engines can likewise share an A frame designation and not share a rating, so the plate matters as much as the frame.
AX33B and the AT frames
AX was released in 2002 as a smaller, lighter and lower-consumption alternative to a Type A of the same output. Type AT builds on the A and AX designs, adding a Miller cycle and electronically controlled cylinder lubrication; the maker lists it as AT33 and AT33L, two models with different rated output and speed. Where the cylinder lubrication is set by feed rate, the cylinder oil feed rate calculator gives the g/kWh from the oil used, the power and the hours, or the litres per day for a chosen rate. Both are cargo-ship and tanker engines, and both carry a version letter that belongs in the request.
K, E, AH and U
The fishing-fleet side of the catalogue, where the company started. Types K and E are fishing-boat and fisheries training-vessel engines designed to run through a reduction gear; Type AH, a four-valve engine, is built for ocean-going purse seiners and high-speed fishing boats; Type U, also four-valve, covers single-shaft, twin-shaft and multi-engine geared installations in ferries and government vessels. Different duty, different wear pattern: a request from this side of the catalogue rarely reads like a Type A one.
UEC LSII, LSE, LSH and LSJ
Akasaka has built Mitsubishi UE two-strokes under a licence dating from 1960; the design now belongs to J-ENG. The generations it lists run from the UEC-LSII, developed from the earlier LA and LS long-stroke engines, through the LSE, on sale from 2006 and since proven in electronically controlled form, to the LSH and LSJ; in 2014 it completed a UEC45LSE-Eco-B2. In March 2026 J-ENG renewed the licence and added its LSJA ammonia-fuelled series. A plate from an older ship can therefore carry an earlier generation letter than the current list shows.
Component groups quoted on Akasaka engines
An Akasaka four-stroke is quoted across the running gear, the cylinder heads and their valve gear, the injection side, the starting and control side, and the pumps and coolers around it; a UEC two-stroke adds the exhaust valve and crosshead groups. Grouped that way, a list covering a scheduled overhaul and an unplanned failure on the same engine stays readable.
- Cylinder liners, liner sealing rings and the anti-polishing rings fitted at the liner top
- Pistons, piston crowns and skirts, piston pins and pin bushes
- Piston ring sets, quoted per cylinder
- Cylinder heads, complete or as reconditioning sets
- Inlet, exhaust and starting air valves — spindles, seats and guides, and on the four-valve AH and U types the exhaust valve cages
- Connecting-rod bearing shells and main bearing shells, with the undersize stated
- Camshaft sections, cams, roller guides, push rods and rocker gear
- Fuel injection pumps, plunger and barrel elements, delivery valves and high-pressure pipes
- Fuel injection valves and nozzles
- Starting air valves, the starting air distributor and its control components
- Governor and actuator components, and speed pick-ups
- Cylinder lubricator components and lubricating quills, mechanical or electronically controlled
- Attached lube oil and cooling-water pumps
- Lube oil, charge-air and fresh-water coolers, thermostatic valves and filter elements
- Gaskets, O-rings, seal rings and complete seal kits
- Top-overhaul and full overhaul kits matched to running hours; on UEC engines, exhaust valve spindles and seats, crosshead and crankpin bearings and cylinder covers reviewed on the UE route
Low-speed four-stroke engine — general arrangement
A licensed photograph of Akasaka equipment was not available at publication, so this technical reference illustrates the general arrangement shared by this equipment class.
Illustrative technical reference, not a photograph of Akasaka equipment or a Vessel Core installed reference — a licensed photo of this maker's equipment was not available. Vessel Core has no dealership, distribution, representation or partnership agreement with Akasaka Diesels Limited; it operates as an independent spare parts supplier.
The plate data that makes an Akasaka line quotable
An A-type frame has stayed in the catalogue for decades, and the same frame has been delivered at more than one rating, so the serial number and the plate rating do more work in review than the type letters on their own.
- Engine type exactly as stamped, with its version letter — AT33L rather than AT33, UEC45LSE-Eco-B2 rather than UEC45
- Engine serial number and build year from the nameplate
- Rated output and speed shown on the plate, in kW or PS and rpm — the same frame has left the works at several ratings
- Which line the engine belongs to: own-design four-stroke or licence-built UEC two-stroke, which decides the catalogue
- Turbocharger make and designation from its own plate, if the line concerns the turbocharger
- Governor type and remote-control system type, if the line concerns speed control
- Emissions build — Tier II or Tier III, and whether a low-pressure SCR or EGR system is fitted
- Cylinder lubrication arrangement — mechanical lubricator or electronically controlled — if the line concerns lubrication
- Part-book page and item number where held, treated as a starting point rather than a conclusion
- Running hours since the last top overhaul or full overhaul, and photographs of the nameplate and of the component in place
Tools for this equipment: the Pt100 and thermocouple reader for the temperature sensors, the pressure gauge selector for the engine gauges and the O-ring size finder for loose O-rings. For an engine on heavy fuel, the CCAI calculator gives the ignition quality of the bunker from the density and viscosity on the delivery note. For a main engine, the admiralty coefficient calculator works out the power needed for a new speed or displacement by the cube law. Where crankshaft deflections are measured, the crankshaft deflection calculator gives the vertical and horizontal figure for each cylinder and a chart of the whole shaft.
How an Akasaka engine RFQ is handled.
An Akasaka line is worked from the plate outwards — type with its suffix and serial first, then which of the two lines it belongs to, then the rating and running hours. Where an old part number exists it is treated as a clue, not as the answer.
Two catalogues under one maker's name
Akasaka's own four-strokes and the UEC two-strokes it builds under licence are separate drawing sets with separate routes. A line is assigned to the right one before it is priced, so a UEC exhaust valve is not chased through a Type A catalogue and an AX liner is not quoted from a UE part list.
Which Akasaka lines survive a verified alternative
Bearing shells, ring sets, valve spindles and seats, seal kits and filter elements are where a verified alternative is usually worth reviewing on price and availability. Cylinder liners, cylinder heads, injection equipment and anything going into a class-surveyed repair normally stay on the OEM route, and on the UEC side that route runs through the holder of the UE design. Where the two routes are not equivalent on a line, the difference is stated rather than smoothed over.
A coastal ship's port stay is read first
Coastal and short-sea tonnage is where most Akasaka plates sit, and its port stays are measured in hours. Lines from a stopped main engine are separated from the scheduled overhaul list so the urgent items are not held behind a full overhaul kit that is being priced at the same time.
Frames listed here are RFQ context
The Akasaka types and UEC generations on this page describe the equipment a request may concern. They do not imply holdings, interchangeability between frames or versions, or any status with the manufacturer.
Handover reviewed against the port call
A liner or a cylinder head is a weight and crating item before it is a catalogue item. Dimensions, weight and whether the berth can take the delivery are checked against the port call and ETA before a handover point is written down. Nothing about the date is treated as settled until it is in the quotation.
EU-registered counterparty
An overhaul kit for a main engine is an order for which most purchasing departments want the counterparty checked before it is raised. Estonian registry 17028043 and VAT EE102773714 are open entries, and the buyer-verification page carries the documents a vetting request usually asks for.
What buyers ask before sending an Akasaka list
What does Akasaka Diesels build, and where are its engines found?
Akasaka Diesels Limited is an independent Japanese builder of ship main engines, with its works at Yaizu, Shizuoka. It began repairing fishing-boat engines in 1910, built its first diesel in 1933 and was incorporated in 1934. Two lines carry the name, both built at its two plants in Yaizu: its own four-stroke engines — the low-speed Types A, AX and AT, and Types K, E, AH and U for fishing vessels, ferries and government vessels — and two-stroke UE engines built under licence, first from Mitsubishi Heavy Industries and now from Japan Engine Corporation. Cumulative production passed 10,000 engines in 2013. The maker lists the A, AX and AT types for cargo ships and tankers, and the UE two-strokes for cargo ships and chemical tankers.
How do you read an Akasaka designation such as A45S or AX33B?
The letters give the family and the number gives the bore in centimetres — read the exact figure off the plate rather than from the name — and the trailing letter marks the version of that frame. Type A runs across several frame sizes and is built as a rule as an in-line six. The licence-built two-strokes read differently: in 6UEC45LSE the leading digit is the cylinder count, 45 the bore in centimetres and LSE the generation, the others being LSII, LSH and LSJ. Copy the designation with its suffix rather than the family letters alone.
Which Akasaka line is which, and what separates them?
Type A is the long-stroke low-speed line; Type AX, released in 2002, is a smaller and lighter alternative at the same output, and Type AT builds on both with a Miller cycle. Types K, E, AH and U are the fishing-fleet and ferry side of the catalogue: K and E for fishing and fisheries training vessels, AH for ocean-going purse seiners, U for ferries and government vessels. The UEC two-strokes are a separate world again, across the LSII, LSE, LSH and LSJ generations. One frame can be offered at more than one rating — the maker lists AT33 and AT33L as separate models — so the figure that matters for a spare part is the one on the plate in front of you, not the family the engine belongs to.
What does an Akasaka RFQ need beyond the engine type?
Three things are missed most often. First, the engine serial number and the plate rating: an A-type frame has stayed in the catalogue for decades and the same frame has left the works at more than one rating. Second, which line the engine belongs to, because Akasaka's own four-strokes and the UEC two-strokes it builds under licence are separate drawing sets with separate parts routes. Third, the turbocharger: it is a separate make with its own plate, and a nozzle ring or a bearing for it cannot be quoted from the engine plate. Running hours since the last overhaul and photographs of the plate and the component finish the picture.
Is Vessel Core connected to Akasaka Diesels?
No, and there is no agreement of any kind. Vessel Core holds no dealership, distribution, representation or partnership agreement with Akasaka Diesels, and quoting a component against one of its designations implies no approval by the maker and no claim of interchangeability.
Why the maker name appears on this page
Maker names help identify equipment and prepare an RFQ. They do not imply any dealership, distribution, representation or partnership agreement between Vessel Core and the manufacturers named on this page; there is none. Akasaka Diesels Limited, Japan Engine Corporation and Mitsubishi Heavy Industries, and the A, AX and UEC designations, are referenced solely so that a buyer can describe the engine on board and the component required.
Send the plate, then the list.
Give the engine type with its version letter, the serial number and plate rating, whether it is an own-design four-stroke or a licence-built UEC, and the components concerned — liner, piston and rings, cylinder head and valves, bearing shells with the undersize, injection equipment, starting air or seals — plus the port and ETA. Where the line sits on the turbocharger instead, send that plate too. The type, serial and rating are read back to you before anything is priced, so a line written as “piston ring” does not come back quoted as one ring when the engine needs a set per cylinder.
