Underwater Mechanic

Matt wears many hats on the boat.  Engineer, electrician, mechanic, refrigeration, fix it man, chef, etc…Today, he wears his underwater mechanic hat. I will show you how he changes the zincs on our starboard prop while underwater. 


We have to have pretty good conditions in order to do this project underwater.  First, little to no wind.  We don’t want the boat swinging around while Matt is trying to “hold on.”  Next, we zero current and shallow waters.  If something is dropped, we want to be able to see it and retrieve it right away.  And lastly, a sunny day with no rain is preferred.


There are lots of things needed to prep.  We dig out the hooka.  What is a hooka?  It’s an underwater breathing apparatus that is operated by a 12v charge.  It is similar to scuba gear but does not require a large tank or BCD.  Matt connects the hooka to a battery and it provides oxygen for him to breath while underwater.  We also prep a bucket, tools and spare zincs.

As an underwater mechanic you need something to put your tools and parts in while underwater.  Matt ties a line from the boat to the buck and submerges it underwater.  He can then put his tools and parts inside the bucket thus reducing the risk of losing them to the sea.

Here is Matt all suited up, the hooka connected to the port engine and the bucket before and after submersion.

Preparing to go underwater

Preparing to go underwater

The Prop

We have two volvo folding props.  We can change the small zincs without having to disassemble and remove the entire prop.  However, in order to get to the larger zinc we have to disassemble and remove three small 1” screws, 3 axels, 3 zincs, 3 blades and the hub just to get access to the large zinc.  Yep, all underwater.

The Process

Our specialist, the underwater Mechanic, gets started.

Matt working on prop

Matt working on prop

First, Matt removes the first small screw, places it in the bucket and then removes the first axel. Middle photo Matt uses the end of the alan wrench to push the axel out. Once these two items are removed the first blade will come off.  Great!

On to the 2nd blade.  Using the same method our underwater mechanic uses the allen wrench to remove the screw, then the axel and then the blade.  This looks easy peasy!

I spoke too soon.  Matt removed the screw (top photo) and used the allen wrench to try to remove the axel.  The first two just look a little tapping.  After several minutes matt starts “jamming” it in with more force and still the axel does not budge (look at his white knuckled fist on lower photo)

He goes to his tool chest for a different tool.  Searching in a black bucket underwater can’t be easy.

Stuck Axel

He grabbed several tools trying to get the axel out – on both sides.  Even using the rubber hammer on each tool he still couldn’t get it out.  He even tried using a clamp and that did not work. Imagine how fun it it so try to hammer something with the water preventing you from using full force.  Poor thing did this for well over 45 minutes banging his fingers several times.

He was relentless on this axel which would not budge. 

After two leg cramps and exhausting all thoughts on how to remove it, he decided to try another time.  So, he put everything back on and called it an exhausting day.

Second Time is Charm

Matt put on his underwater mechanic hat a week later with better success.  He found a spare axel and started with the troubled axel first.  Coming at it fresh, with a better tool allowed him to finally remove the stubbornly stuck axel and prop.  The other two were fairly easy as they were last time.

He brought all the pieces on board to clean and reassemble.  The top photo shows you three things.  The green arrow points to the hub or the main part of the prop.  The blue arrow shows you an axel and the red arrow points to the used large zinc that is being replaced.  The bottom two photos show new and old zincs (large and small).

Matt cleaned up the hub, removed all barnacles, growth and corrosion.   The middle, left photo shows you how small the screws are that Matt has to handle underwater.  The bottom left shows you the size of the axels and the prop blades.  The bottom right photo shows you the numbers that Matt has to match up to the blades. The #1 blade goes in the #1 spot.  Keep in mind, this is all underwater!

After everything was cleaned and assembled in the cockpit he went back underwater to finish the assembly.  The large zinc first, then the hub, then blade #1, axel #1, and screw #1.  Once secured, he repeats the process for blades 2 and 3. 

Project complete!

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