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Engine Hour Tracking: What to Record From Day One
An hour meter counts. It does not remember. A single reading tells you the state of an engine; a series tells you its trajectory, and the series only exists if somebody wrote down the first entry.
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6 min readApex Marine Labs
In this guide 8 parts
Start here
Every marine diesel has an hour meter, and almost every owner can tell you what it reads. Far fewer can tell you what the exhaust temperature was doing at the same load last season, which is the question an engineer will ask before the invoice.
The difference is not diligence. It is that the first entry was never made, and a log that starts in the middle is a log with nothing to compare against.
01 / 08
Why does a series of readings matter more than one reading?
Because a series shows where the engine is going; one reading only shows where it is.
One temperature, taken today, tells you what is happening now. The same temperature, at the same load, taken across a season, shows which way it is moving. The obstacle is that the value of entry one is zero, the value of entry two is almost zero, and the payoff only arrives in the second season, long after most people have stopped.
Which means the discipline has to be cheap. A log that takes twenty minutes will not survive contact with a real season. A log that takes ninety seconds will.
02 / 08
What goes on the reference page?
What your own documentation says, transcribed before the first entry.
Not a table from a forum, not a figure for "a diesel of that size". Your engine, from your manual, in the revision that matches your serial number.
That means the alarm and cut-out points your builder specified, the fluid specifications, the filter part numbers actually fitted, the gearbox ratio, and the propeller specification as installed. Copy them once, note which document each came from, and date the transcription.
This is the step people skip, and skipping it is what makes every later reading ambiguous. Without it you know a number went up. With it you know whether the number going up matters.
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Engine Run Card
The six things to note on every run, with the engine hours on each, a logging rhythm chosen by how you use the boat, a six-line event register and a live drift-per-100-hours calculation.
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03 / 08
When should you take the baseline?
Now, while the engine is healthy.
A commissioning baseline is a set of readings taken when nothing is wrong, under conditions you can reproduce. It is the only thing every later reading is measured against, and it can only be taken once: either now, while the engine is behaving, or never.
Reproducibility is the whole point. Same load, stated. Same sea state, roughly. Same warm-up, timed. A baseline taken at an unknown load is a number with no partner.
04 / 08
What should you note on each run?
Six things, in about ninety seconds, at the same load each time.
| What to record | When | Why it matters | Where in the Diesel Log |
|---|---|---|---|
| Engine hours, with every entry | Every run | Each reading sits on the engine's own clock, and two entries give a rate | Trend entries |
| The load you took the readings at | Every run, once settled | A reading without its load has nothing to compare against | Trend entries |
| Temperatures and pressures, as your gauges report them | At that same load | The series against your baseline is the whole point of the log | Trend entries, against the baseline |
| How the exhaust looked on start-up | At each start | A change from usual is worth a line | Events |
| Any change in smell, sound or vibration | Whenever you notice it | Vague, and the most sensitive instrument aboard; note the change, not the absolute | Events |
| Anything added: oil, coolant, a belt tensioned | When you do it | Consumption between services is a trend in itself | Service |
05 / 08
How often should you log?
As often as the way you use the boat demands.
The method is the same; the frequency is not.
| How the boat is used | What to watch for | How to log |
|---|---|---|
| A weekend boat on a mooring | The risks of standing still: impeller set, fuel ageing, stale coolant | A short entry each outing and a fuller one at lay-up |
| A cruising boat | Hours in bursts, often far from a yard | Every run, so a shift three weeks into a season is on paper while a chandlery is still within reach |
| A liveaboard engine | Running for charging at loads the manufacturer did not have in mind | Charging runs logged separately from hours under way, so neither hides the other |
| A shared or chartered boat | Nobody owns the memory | Every run, with a handover line at the end of each entry |
06 / 08
What does a trend show that a reading cannot?
Drift, which a single reading cannot show.
Many faults build gradually. A heat exchanger fouls gradually, an injector degrades gradually, an alignment moves gradually. Each individual reading sits comfortably within whatever your manual allows, right up until the day one does not.
A series makes the slope visible while each reading is still within what your manual states. That is the entire argument for the log, and it is why the log is worth more than any single measurement in it.
07 / 08
Does an engine log matter when you sell or buy?
Yes: an engine with a legible history sells differently from an engine with an hour meter and a verbal assurance.
It also buys differently: if you are looking at a boat whose owner produces a complete log, you are looking at a different risk from the boat next to it.
You cannot retrofit that. It is made by writing down the first entry.
08 / 08
Frequently asked questions
What should I record in a marine engine log?
Engine hours with every entry, the load you took readings at, temperatures and pressures as your gauges report them, how the exhaust looked on start-up, any change in smell, sound or vibration, and anything you topped up.
How do I check the engine hours on a boat?
Read the hour meter before the engine is started, and write the figure down with the date. Then compare it with the hours on past service invoices, which should rise in step. If the engine has no meter, or the meter has been replaced, say so in the log and note the date you started counting.
How many engine hours is a lot for a boat?
No general figure answers this for your boat, because hours alone do not describe an engine's condition. What tells you more is the history behind them: dated service invoices, a baseline taken while the engine was healthy, and the trend of readings at the same load since. On a boat you are buying, the surveyor or a marine mechanic makes the judgement.
Why take a baseline when the engine is healthy?
Because every later reading is compared against it. A baseline can only be taken while nothing is wrong, under conditions you can reproduce, so the first entries are the ones that make the log useful.
Where do the reference figures for my engine come from?
From your own engine documentation, in the revision that matches your serial number. Transcribe them once, note the source, and compare your readings against them rather than against figures for other engines.
How do you track boat maintenance and documentation?
In one log per system, with the date and engine hours on every line. Record each service with the parts fitted and who did the work, keep invoices with the entry they support, and choose a format you will actually keep up, paper or file. The value comes from entries made consistently, not from the tool.
Every step has its page in the Marine Diesel Baseline & Trend Log. See the record →
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Your next step
The full record: Marine Diesel Baseline & Trend Log. The first entry is the one that costs nothing and decides everything.
See the 41-page logThe document behind this method
The first entry is the one that costs nothing and decides everything.
You already know what your hour meter reads. What you do not have is what it read when the exhaust temperature was still where it should be, at a load you can reproduce, with a witness mark on the page.
The Baseline and Trend Log is built in the order that makes a log usable rather than decorative. A reference page where you transcribe your own manual's figures, with the revision noted beside each line. A commissioning baseline taken while the engine is healthy. Then a deviation log with enough rows to produce a slope rather than a scatter.
It publishes no temperature, no pressure and no interval of its own. Those belong to your engine builder, in the revision that matches your serial number, and the reference page is where they go.
Ninety seconds an outing. The second season is when it starts paying, and the day you sell her is when it pays most.
Marine Diesel Baseline & Trend Log
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See the 41-page logStart the log today, on your own engine
The reference page, the commissioning baseline and the trend log of the Marine Diesel Baseline & Trend Log, fillable in Adobe Acrobat Reader. Your latest entry is set against your baseline as you type.
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