Twisted in the Engine Room

We learn everything about prop shaft coupling removal and how it works in practice. This brings us a step further in one of our big projects but requires a decision.

Dave is befriending the workshop cat

After we had successfully removed the propeller, the dripless seal and the pillow bearing, the shaft coupling now had to be removed. We then will finally be able to remove the shaft and drop the rudder. But you might ask yourself, what a shaft coupling actually is.

What is a shaft coupling?

The propeller shaft transmits the drive from the gearbox to the propeller. For this to happen the shaft is connected to the gearbox by two coupling halves – the prop shaft coupling and the transmission coupling. They are due to their nature located close to the engine, i.e. in the engine compartment. And anyone who has ever been on a sailboat knows that there is usually not much space – same with ours. Since the prop shaft coupling must fit very precisely on the shaft and sit well, the coupling part (unfortunately) ideally does not “just” come off.

This picture shows the two halves of the coupling and the shaft brake
Left: the gearbox coupling; middle: shaft brake; right: propeller shaft coupling

If you are interested in the technical stuff: Further below you can find more technical details about the coupling and the two methods to remove it.

What’s our experience with the shaft coupling removal?

Since we didn’t want to risk a gearbox damage under any circumstances, we built our own tool. To do this, we strayed across the boatyard and searched the waste wood and scrap metal collections. We struck gold with two possibly matching parts, one made of wood and one made of metal.

The manufacture of our tool

Using the shaft brake, which was also removed and had been mounted between the two coupling parts, we were able to mark the holes on the piece of wood, drill them with our Bosch cordless drill and test the finished part directly on the coupling. We got the nuts and bolts we needed from the Ferreteria. Then we transferred the holes to the metal plate, drilled the holes and our tool was ready for the shaft coupling removal.

The wooden model is attached to the coupling
The wooden model

So easy?

No of course not. First the metal plate had to be cut. To do this, we went to the workshop on the boatyard, where we first had to find a power connection. When we then wanted to cut the metal plate with the angle grinder, we noticed that we only had a disc for grinding and not for cutting. So, we asked a few workers at the shipyard who were just building a new steel boat. They kindly cut the plate for us.

The metal plates are cut and now ready to be drilled
The metal plate cut in half ready to be drilled

When it came to drilling holes, we noticed that we had a wood drill bit the right size, but not one for metal. So, Gabe lent us his drill bit of the right diameter. When the first hole was almost finished, Gabe’s drill bit broke off.

Just drill the holes

I remembered seeing a bench drill somewhere in the shipyard – right, among the shipyard workers. So, we asked for their help again. The problem, however, was that they didn’t have a drill bit of the correct diameter either, just a slightly smaller one. Since we were getting desperate, we agreed to the smaller holes. As a thank you, we brought them Swiss chocolate. And we stopped at the Ferreteria to get smaller nuts and bolts. Note that this fun lasted almost a day.

The shaft coupling removal tool ready to use
The shaft coupling removal tool ready to use

Removal of the shaft coupling

Now we could attach our tool and push the shaft out turn by turn. We started with a small ¾ inch nut from our DeWalt Mechanics Tools Kit and Socket Set and exchanged it twice for a longer one. The process of evenly tightening the bolts was tedious and took several hours.

Dave was sitting in an uncomfortable position in the engine compartment and I was lying on the other side of the engine on the floor because the coupling is in a good position for the engine, but not for people. But all’s well that ends well! We were able to remove the coupling and pull the shaft for inspection. Yeehaaw!

We were surprised by the massiveness of our stainless-steel shaft: it is approximately 9ft (275cm) long and has a diameter of 1 ¼ inch (3.2cm).

Dave inspecting the pulled shaft
Our impressive shaft

And how is the shaft doing?

Before we could do anything with the shaft, we had to clean it. Stainless steel protects itself from rusting by forming a thin layer of oxide on its surface. This and all other impurities had to be removed to be able to check it thoroughly for straightness, abrasions and pitting corrosion.

We went to a nearby machine shop together with Dave from SY Cavu whose shaft needed to be inspected too. They’ve unfortunately caught a fishing net in their propeller right in front of the haul out point. As this caused the propeller to jam and forced the engine to stop, there was the possibility of damage to their shaft.

At the machine shop, when the mechanics clamped our shaft in their machine, it was obvious: it wobbled! We kind of knew already beforehand that something was off with it. The knocking noises in the shaft compartment when the engine was in idle and the worn out cutless bearing had indicated it. And now we had the proof.

Straighten the shaft?

Now we have two options: either getting a new shaft or trying to straighten it. The second option costs about a third of the first one, but its success is not guaranteed. In addition, we still have a question mark regarding the existence of our pillow bearing. A quick survey in the Kelly Peterson owner group revealed, that there is no clear answer to it – neither the necessity of this bearing nor the presence.

A shaft can be unsupported for up to 40x its diameter, which means for us for a length of 50 inch (127cm). But before we decide on our next step with the shaft, we are going to bring the pillow bearing to the machine shop to get their professional assessment. Stay tuned!

Housekeeping like in the past?

In addition to such technical things, we also learn a lot of everyday things. For example, neither of us knew in advance how much time we would have to spend on household chores. Every day we spend a total of around 3 – 4 hours cooking, washing up, cleaning, washing, shopping, etc. We both agree that doing the dishes by hand is one of the worst things in the world, in the ranking just after polenta and cold showers.

Our stove by now bothers us so much that I’ve decided to treat myself with a new stove for my birthday. Even tough we manage to make yummy pizza – the other day we even made pizza twice in one evening because we needed more – the stove is useless for most other things except heating water for the coffee in the morning.

Butter Chicken with Naan
Butter Chicken without Chicken

Sonoric weather capers

At the moment it’s still winter time here, but we didn’t think it would be that cold. Last week we woke up several times freezing. And a look at the thermometer confirmed it: it was 6°C (43°F) in the boat. Heater? Nope … We have one, but who doesn’t like to snuggle up in the warm blanket in the evening? And we don’t know when we’ll be able to experience that the next time.

In addition to the fact that it rained every now and then, which is uncomfortable in itself with our leaky dodger, it also winded heavily for a few days. Since Milagros has its stern pointing west and the wind was coming precisely from the west, it hit her with full force and we were shaken. But the stands kept Milagros in place.

Find out how we’re getting on with our other projects in our next blog post.

Waterdrops on the railing in the sunset

As mentioned above, some more technical details about the coupling and the two methods of removing it will now follow.

The right tool to remove a coupling

The coupling consists of two similar halves. One half (the prop shaft coupling) is connected to the shaft, the other half (the transmission coupling) is connected to the gearbox output shaft. The two couplings are connected to each other with several bolts. After disassembling the two parts, there are two different ways to remove the prop shaft coupling: without an additional tool or with an additional tool.

Remove the coupling without an additional tool

In the first method the two coupling parts are reconnected to one another with 2 – 4 temporary bolts. These bolts should be 2 – 3 cm longer than the original ones and be threaded throughout their length. A nut is inserted between the two couplings, the diameter of which is slightly smaller than the shaft. Then the bolts are gradually and evenly tightened crosswise and thus press the shaft out of the coupling. The disadvantage of this method is that the transmission can be damaged if the screws are tightened unevenly.

A drawing of the two couplings and how to remove them
Source: Coxeng

Remove the coupling with an additional tool

For example, a steering wheel puller can be used, or a self-made tool. For the DIY tool you need a metal plate with holes that match the coupling. Then, as with the first method, the plate is mounted to the shaft coupling, a nut is inserted in between and the bolts are evenly tightened crosswise. The advantage of this is that the gearbox cannot be damaged when the coupling is removed.

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2 Comments

Glückliche Gesichter Gratulation, starke Leistung!!
Die Lager-Fluchteinstellung dürfte bei dieser Wellenlänge eine Challenge sein.

Hoi Hans, danke für deinen Kommentar! Ja, das dürfte eine Challenge werden. Aber damit befassen wir uns wenn’s soweit ist. 🙂

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