How to do it

Step-by-step procedures for the marine diesel jobs an owner can reasonably do, and honest diagnostics for the ones you cannot.

Each page answers its question in the first two sentences, then explains the procedure, then says what goes wrong and when to stop and call someone. If a job is beyond a competent owner, the page says so rather than walking you into it.

Before you start anything

The engine is hot, the boat moves, and you are over water. The three constants that make marine work different from the same job on a driveway:

• Never work on a hot engine. Cooling system components hold pressure and scalding coolant, and a raw water circuit that has just been running is hot enough to burn.
• Isolate the batteries before touching anything electrical, and before working near a starter motor or an alternator.
• Close the seacock before opening any part of the raw water circuit, and know how you will close it again if the handle breaks.
• Have a plan for what you drop. A tool in the bilge is an inconvenience; a bolt in the bilge you cannot find is a job not finished.
• If the boat is in the water and the job involves the hull, stop. Stern glands, saildrive legs, seacocks and shaft seals are haul-out work.

When to stop and call someone

This site does not work on boats, so there is nothing in it for us either way. Stop when:

• The job needs the engine running while you are inside it
• You cannot identify a part with certainty
• The fault involves fuel injection pressure, which is high enough to injure
• You are offshore and the fix is not something you can complete underway
• You have tried the obvious thing twice and it has not worked

That last one saves more money than any of the others. Sequentially replacing parts is the most expensive way to diagnose an engine.

The procedures

Every page below is written to be read on a phone with one hand, and to be usable by someone who has not done the job before.