2026 Captain’s Edition
Drivetrain Alignment & Shaft Record PDF
Coupling, Runout & Stern Gear Log
- 24 Pages / 109 Register Lines A4 and US Letter included.
- 518 Live Fields Interactive and 100% offline.
- 6 Calculation Models D1 through D6.
- Instant Digital Access Download links the moment you pay.
A misaligned drivetrain destroys a gearbox, a cutless bearing and a stern tube — in that order, quietly, over two seasons.
It is also one of the few faults on a boat that leaves a paper trail if anyone bothers to keep one. A coupling gap measured at four quadrants, dated, with the hours and the conditions beside it, tells you whether the shaft line has moved. The same measurement taken once and remembered vaguely tells you nothing at all.
This is that record. A reference page you fill in from your own documentation, then measurement sessions kept across years, with a column in every one of them for who held the gauge.
What you receive
A seven-part record for the life of the drivetrain
- A 22-line reference page for the tolerances, torques and specifications you transcribe, with the source and page beside each
- A 16-line preparation page — afloat or ashore, settling time, tankage, mast, temperature: the conditions that decide whether two sessions can be compared
- Six four-quadrant coupling sessions with both variances computed, never an average
- Shaft runout and flange metrology — TIR, face runout, spigot concentricity, with the angular position of the high point
- Cutless bearing play over eight sessions, with the method recorded, because push-pull and dial indicator do not agree
- Six calculation models for TIR, quadrant variance, angular misalignment, parallel offset, deviation and wear rate
You measure. Your yard adjusts.
Reading a dial indicator and slipping feeler gauges into a coupling gap are within reach of a careful owner. Adjusting an alignment is not: it means jacking engine mounts against a shaft line, it is easy to make worse, and the cost of getting it wrong is a gearbox.
So this document is built to sit on both sides of that line. It records what you measured and what your yard measured, with the name in every session. Used before a lift, it tells your engineer exactly where to look. Used after, it proves what changed — and the vibration page, recorded at the same RPM before and after, lets the work be judged on something other than an invoice.
Not one published tolerance. Deliberately.
You will not find a runout limit, a bearing play figure or a torque value of our own anywhere in this document. They differ between builders, between shaft diameters, between bearing types and between gearbox models. A runout limit in thousandths of an inch and one in hundredths of a millimetre are easy to confuse under an engine, and the confusion costs a gearbox. Transcribe yours from your own documentation onto the reference page, record the document, and let model D5 do the comparison.
Two variances, never an average
A drivetrain can sit comfortably inside tolerance on the vertical axis and outside it on the horizontal. Averaging four coupling gaps into one number hides exactly that, which is why this record asks for all four and computes both variances separately — then converts them into an angle and a parallel offset, because angular misalignment and parallel offset are different faults with different causes.
Who it is for
- Owners who have just had an alignment done and want it documented properly
- Owners chasing a vibration nobody can pin down
- Anyone tracking cutless bearing play towards a planned lift rather than an unplanned one
- Buyers and sellers who want the drivetrain history to be more than a verbal assurance
Technical specification
| Product ID | AML-MECH-2026-02 |
| Extent | 24 pages · 7 parts · 6 calculation models |
| Register lines | 109 across reference, preparation, measurement, stern gear and work |
| Interactivity | 518 live PDF form fields — 54 tick boxes and 464 entry fields |
| Formats included | A4 and US Letter, both fillable and print-ready |
| Installations | Shaft drive, any diameter — the document carries no installation-specific data |
| Units | Unit-neutral — you set them and record which you used |
| Offline | No app, no account, no connection required once downloaded |
What it is not
This document records, structures and compares measurements that you or your engineer take. It publishes no tolerance, no wear limit and no torque figure, and it reaches no conclusion about any installation.
Alignment adjustment is not an owner task. Nothing in this document instructs you to slacken, jack or adjust an engine mount, to move a shaft line, or to dismantle any part of a drivetrain. Where a reading falls outside the limit you transcribed, the next step belongs to a qualified marine engineer working from the builder's own procedure for your installation.
Instant download. Your links appear on screen the moment payment clears, and arrive by email within a minute. They do not expire.
2026 Captain's Edition · Revision 1.0 · AML-MECH-2026-02. Apex Marine Labs designs the organisational process behind good seamanship. Our documents record and organise; they do not replace a certified marine survey, a service manual, or a qualified marine engineer.