S1E61. This Is Supposed to Keep WATER OUT?! 😳 | Sailboat Transmission Install
Deep in the cavernous engine room of UV—their 57-foot ketch-rigged fiberglass expedition vessel—the refit team of Sailing UV ( UltraViolet ) tackled one of the most mechanically critical milestones of their multi-year restoration: installing the primary marine transmission and rebuilding the propeller shaft sealing assembly. Undertaking a comprehensive refit to prepare the heavy-displacement ketch for an eventual global circumnavigation, every propulsion subsystem must meet rigorous offshore standards.
Installing a marine gearbox on a 57-foot vessel is rarely a straightforward bolt-on task. Between hoisting the heavy transmission into a cramped bilge, achieving precision face-to-face flange alignment with the propeller shaft coupling, and rectifying decades of questionable previous-owner modifications, the project exposed serious vulnerabilities in the vessel’s underwater integrity.
Uncovering Questionable Shaft Seal Hardware
The primary barrier preventing seawater from entering a vessel along the spinning propeller shaft is the shaft seal or stuffing box. While preparing the forward shaft coupling, the crew inspected the existing dripless seal locking collar and were shocked to discover a stripped, corroded Phillips-head machine screw holding the assembly in place.
In standard marine engineering practice, shaft seal collars utilize hardened stainless steel Allen set screws locked in tandem (a primary screw backed by a jam screw) directly into dimpled recesses on the shaft. Finding a lightweight, stripped fastener securing an assembly tasked with keeping the ocean out of a 57-foot hull highlighted the peril of uninspected legacy refit work:
- Fastener Stripping & Extraction: The improper Phillips fastener was heavily deformed, requiring careful extraction techniques to avoid scoring the stainless propeller shaft.
- Collar Retention Failure Risks: If a shaft seal retaining collar slips along the shaft while underway, water pressure can push the seal open, causing catastrophic bilge flooding.
- Proper Marine Rectification: Cleaning the shaft surface, re-tapping the retaining collar threads, and installing marine-grade 316 stainless set screws with thread-locking compound.
Gearbox Mounting and Driveline Alignment
With the shaft sealing collar secured, the crew maneuvered the rebuilt marine transmission into the engine compartment, mating the input spline to the diesel engine’s damper plate. Once bolted to the bellhousing, achieving exacting alignment between the transmission output flange and the propeller shaft coupling became the central technical challenge.
Shaft alignment tolerances on heavy cruising yachts must typically remain within .002 to .003 inches around the circumference of the coupling flange. Even minor angular or parallel misalignment introduces cyclic vibration that destroys cutless bearings, overheats transmission seals, and can fracture the output shaft under prolonged offshore motoring.
Preparing the Ketch for Circumnavigation Readiness
Restoring a heavy-displacement 57-foot ketch demands systematic patience. By rectifying sub-standard hardware before launch and establishing true mechanical alignment, the UV crew eliminates potential points of failure that could imperil an ocean crossing. Each completed mechanical milestone brings the classic fiberglass vessel one step closer to leaving the yard and beginning its voyage around the world.
Propulsion and Shaft Refit Specifications
The mechanical parameters and refit details for UV’s transmission and driveline overhaul are detailed below:
| Refit Element | Specification / Observation | Marine Engineering Role |
|---|---|---|
| Vessel Model | 57-Foot Ketch-Rigged Fiberglass Cruiser | Heavy-displacement offshore tank undergoing circumnavigation refit |
| Primary Project | Transmission Installation & Shaft Alignment | Restoring main propulsion reliability and vibration-free drivetrain power |
| Shaft Seal Defect | Stripped Phillips fastener in retaining collar | Improper legacy hardware risking collar slippage and bilge flooding |
| Corrective Action | Thread chase & dual 316 stainless set screws | Positive mechanical lock dimpled into stainless propeller shaft |
| Coupling Tolerance | .002" to .003" Flange Alignment Target | Prevents output bearing wear, transmission failure, and shaft fatigue |
| Long-Term Objective | Full System Circumnavigation Readiness | Systematic replacement of all questionable legacy components |
Frequently Asked Questions
Sailing UV is refitting a 57-foot ketch-rigged heavy-displacement fiberglass cruising yacht for an eventual circumnavigation.
The shaft seal collar was held by a stripped Phillips-head machine screw instead of proper dual stainless Allen set screws locked into the shaft.
Misalignment exceeding .002 to .003 inches causes destructive vibration that rapidly damages cutless bearings and transmission output seals.
The crew extracted the damaged fastener, re-tapped the retaining collar threads, and installed proper 316 stainless set screws dimpled into the shaft.
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We’re FINALLY installing the transmission in UV… and of course, nothing on a 57-foot project boat goes according to plan. 😂
Welcome aboard UV, our 57-foot ketch-rigged fiberglass tank that we’re slowly bringing back to life and refitting for an eventual circumnavigation.
This week, there’s no long introduction—we’re getting straight to work.
The mission sounds simple: somehow maneuver a roughly 110-pound marine transmission into UV’s engine room, get it onto the engine, line everything up, reconnect the prop shaft, and move one HUGE step closer to firing the boat up.
Simple, right?
Yeah… about that. 😂
With a chain hoist overhead and a block-and-tackle setup controlling the other end, I start lowering the transmission into place. There’s just one problem: there isn’t much room, the transmission wants to swing everywhere, and all I can think about is what happens if something lets go and I suddenly have a transmission-sized hole in the boat.
Eventually we get it where it belongs—but then we run straight into the #1 rule of boat work:
Before you can do the thing you came to do, you have to do five other things first.
The transmission oil cooler has to move. The flywheel cover has to come off. The prop shaft has to move. The bearing needs attention. The floor I built suddenly makes everything nearly impossible to reach…
…and then I discover something considerably more interesting.
The clamp on the shaft seal has completely failed.
You know—the hardware connected to the thing whose job involves KEEPING THE OCEAN OUT OF THE BOAT. 😳
Even better, I discover that what I had been calling a dripless shaft seal is actually a lip seal—something I knew basically nothing about.
Looks like we’re learning together.
That discovery turns this transmission installation into a much bigger job, and unfortunately we hit the end of this episode before getting everything bolted together and firing UV up.
So yes…
TO BE CONTINUED.
Next episode, we’ll finish getting the transmission into position, reconnect everything, deal with the shaft setup and—if everything cooperates—fire UV up and see if all this work actually paid off.
Stick around until the end of this one for a little decompression session with Violet and me putting around the bay in the tender. Sometimes after fighting a boat all day, that’s exactly what you need.
If you enjoy real-world boat work, DIY repairs, marine systems, refitting an old 57-foot sailboat and watching me figure things out as I go, hit SUBSCRIBE and come along for the ride.
Our ultimate goal is to get UV completely refitted and head out on a circumnavigation. There’s a mountain of work between here and there—and you guys get to see all of it.
Welcome aboard Sailing UV. ⚓
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🔧 TOOLS & GEAR USED IN THIS EPISODE
A few of the tools you see me using aboard UV:
🔧 Milwaukee Socket Set:
https://link.amazon/B08kJlYmJ
🪛 Milwaukee 13-in-1 Screwdriver:
https://link.amazon/B03NHoAUv
🔦 Work Light:
https://link.amazon/B099atFF3
Amazon Affiliate Disclosure: As an Amazon Associate, Sailing UV earns from qualifying purchases. Using our links doesn’t cost you anything extra, but it helps put a little money back into UV and the refit. Thank you!
Unfortunately I had to hit you guys with the dreaded TO BE CONTINUED… 😬 Next episode we finish the transmission installation, get everything connected and hopefully FIRE UV UP!
👇 QUESTION FOR THE CREW:
What would have worried you more—110 lbs of transmission hanging over the boat, or discovering that broken clamp on the shaft seal?
And if you haven’t already, SUBSCRIBE and come aboard. We have a ridiculous amount of work coming on UV as we get her ready for circumnavigation. ⚓🌎
Thanks for being here.
— Jonathan & Violet 🐾 | Sailing UV
#SailingUV #SailboatRefit #BoatRestoration #BoatRepair #Sailboat #BoatLife #DIYBoatRepair #MarineDiesel #MarineTransmission #SailboatRestoration #BoatProjects #Liveaboard #SailingLife #Circumnavigation #VioletTheDoberman #fyp #dream #pets
Sailing UV ( UltraViolet )
Jonathan sold everything in Ohio to purchase a neglected 1996 Henry Morgan 57 in the Northern California. Operating under the channel Sailing UV, he and his 100lb Doberman, Violet, are currently executing a massive technical refit near Sausalito. As of 2026, the project focuses on heavy electrical diagnostics and advanced gyro stabilization before attempting a global circumnavigation.
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S1E61. This Is Supposed to Keep WATER OUT?! 😳 | Sailboat Transmission Install Location
- Sailing UV Refit Yard, Florida, USA (29.8947,-81.3145)
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