Manuals for Dong-I Marine Transmissions (Gearboxes)

Dong-I, also known as D-I Industrial is a South Korean manufacturer of marine transmissions. The company was founded in 1990.

Dennison Berwick at launch of Marine Diesel Basics 1 in Toronto, Canada

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3 simple steps to make your diesel system reliable and robust

STEP ONE  - Get the manuals for your equipment

Owner, Workshop and Parts Manuals are important documents that should be part of every vessel's library. They contain the detailed information necessary for safe operation, maintenance and correct servicing.  

The manuals on this page are provided for public information and education and can be downloaded for free.  All copyrights belong to copyright holders stated in the documents.

congratulations - by downloading these free manuals you are taking an important step towards making your engine more reliable and robust.


STEP TWO - regular maintenance

Simple, regular maintenance is the easiest, quickest and cheapest way to avoid problems and accelerated engine wear. Most expensive repairs start from a lack of basic maintenance or ignoring small warnings. The work is not difficult - it just needs to be done.

The purpose is so that we can enjoy our boat for all the reasons we bought her. Trust yourself. Do the work regularly and be methodical.


Download free checklists here

if you need clear, easy-to-understand help

300+ drawings

Seeing is Understanding

Marine Diesel Basics 1
Maintain, Winterize and Recommission

•  explains all parts of the marine diesel system - fuel,
lubrication, breathing, electrics, stern gland, propeller etc.
•  140+ tasks, 300+ drawings, 222 pages
•  tasks are fully explained with clear drawings and minimal text
•  all tools & supplies needed are illustrated for each task
•  paperback US$15.99 £10.99 €12.99
•  ebook (kindle, kobo, ibooks, google, epub) US$9.99


STEP THREE - keep a Maintenance Logbook

Keep a detailed and accurate record:

  1. all the work done on your diesel system - what, when  & by who
  2. inventory of serial numbers, component descriptions
  3. early warning of potential problems
  4. time and details of any changes in performance

Use a notebook or use your iPad, tablet or desktop and record the information in an editable PDF directly as you work.

click to enlarge

Maintenance eLogbook

If you've every struggled to keep a logbook, this editable eLogbook may be exactly the help you need.

- "fillable form" PDF
- clickable checklists
- write, edit  details of all tasks completed
- 40+ drawings to help inspections
- all common measurements with live calculators
- just $7.99 196 pages

"the Perfect Logbook" - verified purchaser


Dong Marine Transmission Catalog

Marine Transmission


14 pages
publ. February 2009


3 MB file

D-I DMT 18A-K marine gearbox Gearbox Service Parts List

Service Parts List



13 pages
publ. 2017


3 MB file

D-I Industrial 25AL marine transmission Service Manual

Service Manual



38 pages
publ. September 2017


3 MB file

D-I 25AL marine transmission Data sheet

Marine Transmission Data



1 page
publ. September 2007


<1 MB file

D-I 25AL marine transmission 1.64 Ratio Drawing

Marine Transmission Drawing

25AL  ratio 1.64

1 page
publ. June 2018


< 1 MB file

D-I 50A marine transmission Data

Marine Transmission Data



1 page
publ. September 2017


<1 MB file

D-I 50A-I marine transmission Service Parts List

Service Parts List



14 pages
publ. 2017


3 MB file

D-I DMT90A marine transmission Service Parts List

Service Parts List



14 pages
publ. 2017


3 MB file

D-I Industrial DMT 90A marine transmission Diagram

Marine Transmission Data



1 page
publ. September 2017


<1 MB file

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