The ESI shaft service course: measuring & Glide ordering, stern-tube & strut inspection, cutless bearings (press & fold-out, blind pullers, induction heat), shaft seals (Glide lip first, Lasdrop & Tides), packing gland, coupling paint & alignment, and when to escalate — with ABYC P-6-2021 alerts and gated how-to videos.
Before you start
The ESI shaft technician course — coupling to prop. Measuring and ordering (Glide), stern-tube and strut inspection, cutless bearings (press & fold-out, blind pullers), pullers and induction heat, shaft seals (Glide lip seal first, Lasdrop & Tides as alternates), the packing gland, coupling paint and alignment, and when to escalate. ABYC P-6-2021 is called out throughout as ⚓ alerts. Some chapters have a required video — watch it to unlock the procedure. A final exam unlocks your certificate.
Caliper to the part; order the Glide way; size hose down.
Lip vs face seal; install tool, clamps, the right lube.
Structural risk → stop and escalate to the lead tech.
Chapter 1
The whole job, end to end.
This course covers the driveline from the transmission coupling to the propeller: the shaft coupling, shaft, stern tube / shaft log, shaft seal (dripless or packing), cutless bearing, strut, and prop. Get any one wrong and the boat leaks, vibrates, or loses drive.
The whole system is governed by ABYC P-6-2021, Propeller Shafting Systems — it covers shaft material and sizing, struts, stern/cutless bearings, shaft seals, shaft logs, couplings and props. We call out the relevant P-6 points as ⚓ ABYC alerts throughout.
Chapter 2
Measure right or order wrong.
Almost every part you order — shaft, bearing, seal, hose — comes from a caliper reading. A wrong measurement is a wrong part and a second haul.
Chapter 3
What Glide needs, exactly.
We lead with Glide (we're a dealer). Order with the exact format Glide wants — wrong format, wrong part.
| Ordering | Give Glide |
|---|---|
| Bearing | Shaft size × Stern-tube ID × L (length noted only if tight; otherwise not necessary) |
| Dripless seal | Shaft size × Stern-tube ID |
| Seal sizes | 0.75″–6.00″ in ¼″ increments · Metric 25 / 30 / 40 / 50 mm |
| Hose sizes | 1.50″–7.00″ in ¼″ increments (also 2.625″) |
Glide contact: Tim Creighton II, Operations Manager, Glide Bearings & Seal Systems, 6090 Alden Nash Ave SE, Alto MI 49302 — O: 616-868-9730 · C: 616-706-8962.
Chapter 4
Before new parts go in, judge what's there.
New bearings and seals only last if what holds them is sound. Inspect before you order.
Slide the old hose/seal forward and confirm the shaft sits centered in the tube with equal clearance all around. If clearance is visibly uneven, the boat needs re-alignment before any new seal goes on — installing on a misaligned shaft causes premature wear and voids warranty.
Chapter 5
Which bearing, and why it matters.
The cutless bearing is a water-lubricated rubber bearing (grooved for water flow) that supports the shaft at the strut or stern tube. The grooves let water in to lubricate and carry grit out.
Chapter 6
Press it, or fold it out.
With the shaft out: ≥½″ threaded rod, four nuts, and thick washers (thin ones dish and flare the bearing). Grease between two washers (smooth sides together) so they spin freely. Lube the bore and bearing with bar Ivory soap (it dissipates and won't compromise the press fit — never grease). Start the bearing perfectly straight, then draw it through; press the new one in flush. A socket-and-bolt setup works the same way on smaller bores.
Where the bearing is in the dead wood or a housing you can't reach from behind, you can't push it through — use a blind / internal puller (expanding collet that grips the bore and draws the bearing out toward you). Same press-in on the new one.
Two fits matter, and they're different:
Fit guidance: Glide Marine Bearing / GLIDE-100 install options; Steve D'Antonio Marine Consulting & industry cutless-bearing fit references.
Method reference: Maine Sail, “Replacing a Cutless Bearing (photo-heavy),” Sailboat Owners Forums (technique only; ESI photos used).
Chapter 7
Get the prop, coupling and bearing off without damage.
Most shaft work is really removal — and the right puller saves the part.
A coupling rusted to the shaft taper/key won't pull cold. An induction heater heats the coupling fast and locally — it expands off the shaft without an open flame on the boat. Heat, then pull. (A torch is a last resort and a fire risk near a hull.)
Chapter 8
Two ways to keep the water out.
Every modern dripless is one of two designs. Know which you're holding.
| Lip seal | Mechanical face seal | |
|---|---|---|
| How it seals | A flexible lip rides on the shaft (or a sleeve) | A spinning stainless rotor presses on a carbon face |
| Brands | Glide (GMS / GMSS), Tides | Lasdrop (Gen2 / Elite / Dry), PSS / PYI |
| Needs from the shaft | A smooth, unworn running surface (the lip burnishes a track) | A clean shaft; the seal faces do the work, not the shaft |
| Wear | Lip wears a track; relocate to clean surface or sleeve | No shaft wear; carbon/stainless faces wear slowly |
Because the lip seals against the shaft, the shaft running surface must be smooth and unworn. Set the seal on a clean section (Glide's 5–6″ running location), and if the shaft is dished where the old seal rode, relocate the new seal to clean shaft. This is exactly why we check shaft condition before quoting (it ties back to the repower drivetrain conversation).
Chapter 9
The Glide GMS / GMSS, step by step.
Glide comes in two models: the GMS (standard) and the GMSS. They install the same way; the difference is that the GMSS carries a field-replaceable spare seal — swap it without pulling the shaft (Chapter 15) — while the standard GMS does not. Confirm which is on the boat, and lead with the GMSS when the customer wants the field-repair option.
Watch the Glide install before the step-by-step unlocks.
Chapter 10
The Lasdrop Gen2, and where a face seal differs.
Watch the Lasdrop install before the steps unlock.
Chapter 11
Traditional packing, done right.
Plenty of boats still run a traditional packing gland (stuffing box) — flax / PTFE rings compressed around the shaft. Done properly it's reliable and cheap; done lazily it scores the shaft or floods the bilge.
Chapter 12
Off clean, painted, back on right.
Mark the coupling-to-shaft orientation and key position. Induction-heat the coupling (Chapter 7) and pull it off the shaft taper/key — never beat it off cold.
Clean the coupler to bare metal, prime it, then spray it ESI blue. A primed, painted coupler resists the rust that seizes it to the shaft and looks like ESI did the work.
Fit the key, slide the coupler home to its mark, and torque the fasteners to spec. New couplings get faced to the shaft so the flange runs true (this feeds straight into alignment).
Not every coupling is keyed onto a taper. Some are secured by an internal nut — a shaft nut inside the coupling bore, or a clamp / split coupling that pinches the shaft. You can't heat-and-pull these blind: identify the type first, then access and back off the internal nut before any puller comes near it.
Chapter 13
Run true, lock it, done.
Preferred sequence: rough-align out of the water first, then re-align afloat. Set it close on the hard (better access), then — with the boat back in the water and settled a day or two with fuel and water aboard — do the final alignment. The hull flexes between the stands and the water, so the in-water alignment is the one that counts.
Slide the two coupling halves together by hand and run a finger or straightedge around the rim: the flanges must be concentric, with no step. Adjust the engine side-to-side and in height until the rims are flush all the way around.
If a point reads large, adjust the engine mounts (mount nuts raise/lower; shift side-to-side). After every adjustment, rock the engine to settle it in the mounts, then re-check all four points. Work it down until every point is in tolerance and rotation doesn't change it.
Bolt the coupling up and apply blue (medium) Loctite at the final torque — holds against vibration, still serviceable.
Chapter 14
Know the line between persistence and damage.
Some come off easy; some fight. The skill is knowing when more force makes it worse.
Stop and get the lead technician when:
Chapter 15
Read the wear, know the intervals, fix it fast.
Knowing when a part is done — and being able to swap it fast — is half of shaft service.
| Part | Interval / life |
|---|---|
| Glide lip seal | Years on a smooth shaft; replace the element when the lip track wears. GMSS carries a field-replaceable spare; the standard GMS does not. |
| PSS / PYI bellows | Inspect twice a year; replace every 6 years (Type A), 8–10 yrs (PRO / Type B) — with O-rings, set screws & clamps. Keep clear of venting batteries (acid vapor ages the rubber). |
| Lasdrop faces | Long life; rotate an idle shaft every two weeks to avoid face pitting. |
| Packing | Re-pack each haul / season as it stops holding the drip. |
| Cutless bearing | At the wear limit above — and any time the shaft is out (cheap insurance). |
The Glide GMSS (and PSS) carries a spare seal you can install without pulling the shaft — about five minutes. The standard Glide GMS does not have the spare seal, so confirm which model is fitted. Where the GMSS is installed, keep a spare aboard: if a lip weeps away from the dock you relieve the housing, slide it, swap in the spare element, re-clamp to spec, and you're sealed — no haul-out. A real selling point and a fast fix.
Chapter 16
How we work is part of the work. This applies to every job.
Skill gets the job right; discipline gets it done profitably and hands the customer a boat that's better than we found it. These habits run through every ESI field job.
Before you walk to the boat, plan the job and gather the tools, parts and equipment you'll need. Think it through end to end and stage it. A planned job is a fast job; a forgotten tool is a trip you didn't have to make.
Use a cart for each job. Stage your tools, parts and consumables on it so everything travels with you to the boat and stays in one place — not scattered, and not back in the shop.
Every trip back to the shop is unbillable time the customer doesn't pay for and the job eats. Walking costs money. Keep your tools organized and within reach so you're working, not searching or fetching.
Count the extra trips you make to the shop and record those numbers. Trips per job, tracked over time, show where pre-planning is slipping and where we can tighten up. Honest numbers, every job.
No job is done until it's to spec, cleaned, and inspected by the lead. Leaving the engine room or cockpit dirtier than we found it is never acceptable.
ESI runs on Kaizen — continuous improvement. Small better-ways found on the boat, captured every day, compound into a faster, sharper shop. That only works if you write it down.
Field reference
Field-tested: the symptom, the usual cause, and the fix. Always diagnose before you replace parts.
| Symptom | Likely cause | Fix |
|---|---|---|
| Driveline vibration under way | Shaft runout out of spec, misalignment, worn cutless, or a damaged prop | Measure runout, re-align afloat, replace the cutless, check/balance the prop |
| Dripless seal weeping | Bellows perished, carbon faces worn, scored shaft, or not burped at launch | Burp the seal on launch; replace bellows & faces on schedule; polish or replace the shaft |
| Cutless bearing knock / rumble | Worn beyond the play limit or spun in the strut/log | Replace the cutless; confirm the strut bore and set-screw fit |
| Coupling face runout high | Dirt or burrs on the faces, bore mismatch, or a bent shaft | Clean and stone the faces, re-face/re-bore the coupling, verify shaft straightness |
| Traditional stuffing box runs hot | Packing over-tightened | Re-set to roughly 1–3 drips/min under way; re-pack if glazed |
| Alignment drifts after splash | Hull settles and relaxes in the water | Always do the final alignment afloat, about 24 h after launch |
| Shaft or prop pitting | Stray current or galvanic loss; missing shaft brush/anode | Fit and clean the shaft anode & brush, check bonding, hunt stray current |
Final certification
A short check ran at the end of each chapter. Pass this final at 80% to unlock your certificate.
