Record each engine's total-hours reading after a trip and whenever it is serviced. A notebook, spreadsheet, or maintenance app can all work. The essential information is the engine, date, reading, and work performed.
To find the next hour-based service point, add the task's interval to its last-service reading. Then compare that with the calendar deadline. Here is a simple way to set up the log and do the calculation.
Where to find engine hours
Look for a dedicated hour meter, a small hour display within the tachometer, or a total-engine-hours page on the electronic engine display. On a multi-engine screen, select each engine separately.
Check what the number measures before copying it:
Swipe or scroll to see all columns.
| Reading | What it tells you | Use for maintenance |
|---|---|---|
| Total engine hours | Accumulated hours reported by that meter or controller | Normal reference, with any meter/controller replacement noted |
| Trip hours | Time accumulated since a trip reset | Useful for a trip, but does not establish lifetime hours |
| Service counter | Time since a service reset, or time until a reminder | Useful reminder; keep the actual completed work separately |
| Generator hours | Generator operation | Track against generator tasks, separately from propulsion |
Some engines can provide hours through a controller or dealer diagnostic tool. Older installations may rely entirely on a separate meter. A replacement meter or controller may contain only part of the engine's history.
For a documented example, Honda's BF115D/BF135A/BF150A manual, printed page 34 describes a resettable maintenance notification counter. Resetting it after service does not establish lifetime hours.
A simple engine-hours log
Use one row per piece of equipment. These are fictional readings:
Swipe or scroll to see all columns.
| Date | Equipment | Total-hours display | Note |
|---|---|---|---|
| September 1 | Port engine | 812.4 | Before weekend trip |
| September 1 | Starboard engine | 806.1 | Before weekend trip |
| September 8 | Port engine | 818.0 | After weekend trip |
| September 8 | Starboard engine | 811.7 | After weekend trip |
| September 8 | Generator | Unknown | Reading not collected |
In this example, each engine accumulated 5.6 hours: 818.0 minus 812.4 for port, and 811.7 minus 806.1 for starboard. Keep both readings even when the increase is identical.
The boat did not run for 11.2 hours just because both engines operated for 5.6 hours. Adding engine readings together creates a different number that cannot schedule service for either engine.
A consistent habit is enough: photograph the displays at the end of a trip, then enter the readings while the trip is fresh. You do not need a detailed route log or a reconstruction of every old voyage.
Calculate hours and time until service
For a recurring task, use its actual manufacturer interval and the last documented completion:
- Next service reading = last-service reading + hour interval.
- Hours remaining = next service reading − current reading.
- Next service date = last-service date + calendar interval.
Use the first limit reached.
For illustration, suppose a task has an interval of 100 hours or 12 months, and was completed at 720 hours on April 10, 2026. Its next limits are 820 hours and April 10, 2027.
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| Current situation | What it means |
|---|---|
| 805 hours on March 1, 2027 | 15 hours remain; calendar deadline is April 10 |
| 825 hours on March 1, 2027 | 5 hours beyond the hour limit |
| 805 hours on April 15, 2027 | Calendar limit has passed, despite 15 hours remaining |
This is a calculation example, not a universal oil-change interval. For actual schedules, see the Cummins 6CTA guide, Cat 3208 guide, or outboard guide.
Some schedules also use fuel consumption or special operating conditions. Keep those limits when they apply.
Use the log before a trip
Compare the remaining hours with the running you expect. If a task has 15 hours left and the trip is likely to add 20, arrange that work before leaving or plan a suitable service stop.
A calendar estimate can help with booking: at roughly five engine hours per week, 15 hours remaining is about three weeks. Treat that as a planning estimate. The actual meter and calendar limits still determine when the task is due.
Check open repairs and new symptoms as well. A current oil-change entry does not resolve a fuel leak or an overheating problem.
Use the before-trip boat maintenance checklist for pumps, leaks, steering, and the rest of the boat. If Catalina is your destination, the Avalon Harbor mooring guide covers getting a spot, handling the sand line, and getting ashore.
What to write when service is completed
A useful entry names the task rather than saying only "engine serviced." For example:
Port engine — oil and filter changed — September 8, 2026 — 818.0 hours. Oil specification and filter listed on attached invoice. Checked for leaks after service.
Keep the engine position, completion date, actual reading when known, materials or parts, and invoice/work description. Record pump inspection as inspection and impeller replacement as replacement; those are different facts.
If both engines receive the same work, record it for both with their individual readings. One invoice can support both entries when it identifies both engines and the work.
A reminder reset belongs after the work is completed and recorded. Resetting a counter alone should not become your only evidence of maintenance.
Missing readings or old service records
A known service date remains useful. If an invoice says the port oil was changed on June 2 but gives no hours, retain June 2 and leave the reading unknown. You can calculate a calendar deadline while the hour-based deadline remains unresolved.
If you have a current meter reading but no previous service record, save the current reading. It does not establish that a service was completed today or reset every task's clock. Have unknown important work assessed and document any service actually done.
Do not split an old combined engine-hour total between engines, or copy the port reading to starboard. Neither produces a verified individual reading. Collect each engine's next real display reading instead.
Replaced meters and readings that go backward
Record the changeover date, old reading if known, and new meter's starting reading. Preserve the work order or photographs.
For example, if an old meter read 1,240 hours, the replacement started at zero, and no running time was lost at changeover, a new reading of 36 hours supports an adjusted total of 1,276 hours.
Label whether entries use the displayed reading or a documented adjusted total. Keep that basis consistent when comparing with old service entries. A service recorded at 1,220 lifetime hours cannot be directly compared with 36 hours on the replacement meter.
If the old reading is unavailable, lifetime hours remain unknown. Record the new meter's readings and future work from that point. If a reading unexpectedly drops without a known replacement, check the selected engine and display mode before changing the history.
Sources and scope
- Honda BF115D/BF135A/BF150A owner's manual: printed page 34 explains the maintenance notification counter; pages 67–68 show an hours-or-calendar schedule.
- Honda BF150 manual selector: match the installed motor to its serial-range documentation.
- Identify your boat's engine if you need to match a display, equipment record, or manual to the right motor.
Updated September 14, 2026. Log entries, due-date calculations, and trip estimates above are worked examples, not real owner records or guarantees of engine condition.