Changing prop underwater?

[Ric]

My boat is booked to come out of the water in two days, with no other slot for a month or two, and my new folding prop has not yet arrived...

As a fallback plan in case the prop doesn't arrive tomorrow, I'm considering taking off the old prop while the boat is ashore, then getting a tow without prop back to my berth. Once the new prop arrives, I could possibly dive to fit it (got all the kit etc).

Is this feasible? I've never changed a prop on dry land, so am not sure what is involved.

 

[Spyro]

My boat is booked to come out of the water in two days, with no other slot for a month or two, and my new folding prop has not yet arrived...

As a fallback plan in case the prop doesn't arrive tomorrow, I'm considering taking off the old prop while the boat is ashore, then getting a tow without prop back to my berth. Once the new prop arrives, I could possibly dive to fit it (got all the kit etc).

Is this feasible? I've never changed a prop on dry land, so am not sure what is involved.

Taking the old one off will be more difficult that fitting the new one.You may need some type of puller. If you get the old one off you will see how to fit the new one. Should be simple enough as long as you have the correct size spanner for the prop nut and can get enough force on it. Biggest worry would be loosing the keyway slug if it has one. It might also have a split pin which will be a bit fiddly underwater.
If you are on your own remember to lock the shaft before diving under.

Common arrangement

 

[earlybird]

A puller, or similar, will almost certainly be required, but as that part of the job is on dry land it shouldn't be too difficult.
Refitting under water must be possible, but folding props aren't quite so straightforward as the fixed variety. The blades normally have to be fitted after the hub has been assembled onto the shaft. This involves fitting pivot pins and locking screws so can be quite fiddly, with great potential for dropping a vital small component.
It's also possible that loctite might be specified for grub-screws, which won't be possible underwater AFAIK.
Best of luck!

 

[rich]

Don't forget to tie a bit of string to your tools,

 

[Spyro]

A puller, or similar, will almost certainly be required, but as that part of the job is on dry land it shouldn't be too difficult.
Refitting under water must be possible, but folding props aren't quite so straightforward as the fixed variety. The blades normally have to be fitted after the hub has been assembled onto the shaft. This involves fitting pivot pins and locking screws so can be quite fiddly, with great potential for dropping a vital small component.
It's also possible that loctite might be specified for grub-screws, which won't be possible underwater AFAIK.
Best of luck!

I forgot about the intricacies of a folding prop....maybe not so easy.

 

[ccscott49]

My boat is booked to come out of the water in two days, with no other slot for a month or two, and my new folding prop has not yet arrived...

As a fallback plan in case the prop doesn't arrive tomorrow, I'm considering taking off the old prop while the boat is ashore, then getting a tow without prop back to my berth. Once the new prop arrives, I could possibly dive to fit it (got all the kit etc).

Is this feasible? I've never changed a prop on dry land, so am not sure what is involved.[/QUOte

As you are fitting it, a decent diver should be able to manage it, lots of more difficult work is undertaken underwater by lots of divers. Tightening the fixing nut might be problematic, but as long as the shatft/prop can be locked and you can use the hull etc to lever against, then, I dont see any reason it can't be done with a feathering prop, I've changed about 10 props underwater including removing them, but admittedly none feathering.

 

[Searush]

I suppose you are in the Med, cos on the other side of France, the logical thing would be to dry out against a quay to do it. Its as easy as doing on land, just wear wellies!

Even so, is there anywhere you could go aground for a tide & do it. It only needs a tidal drop of 0.5mtr to keep the boat steady & heeling with the prop just below the surface & you with your feet on the ground. Simply stand up to breathe. You should be working at about chest height & be able to see what you are doing clearly.

 

[vyv_cox]

I have removerd a Stripper underwater, replaced the bearings and rebuilt it. Only dropped one spanner, which fortunately was attracted to a magnet.

 

[Sailfree]

Sea bottom would also be a factor.

Drop something in Silt and you will never find it. I carefully marked the spot and dived in Morlaix but never found my mobile phone!!

 

[earlybird]

Sea bottom would also be a factor.

Drop something in Silt and you will never find it. I carefully marked the spot and dived in Morlaix but never found my mobile phone!!

You should have rung its number!

 

[Talulah]

If the only reason you are coming out is to fit the prop I would cancel.
Firstly, the new prop may not arrive.
If it's late you won't be able to use the boat.

You don't say which make of feathering prop or how many blades.
A 2 bladed is much easier to put together than a 3 bladed.
With a 3 bladed you really need (not essential) an extra pair of hands as you try to get everything aligned and in position on the hub.

 

[Bosun Higgs]

Is this feasible? I've never changed a prop on dry land, so am not sure what is involved.

Getting the prop off is the difficult bit - putting on a fixed prop is easy. I have never tried wielding a socket set, greasing a shaft etc whilst in diving gear but if you feel confident of that bit and the water is clear-ish, then go for it.

If the prop is a folder or featherer that is much more intricate to assemble I would still have a go. After all, your fall back is to have the boat out a second time which you will have to do if you dont try and install underwater anyway.

 

[maxi77]

It certainly should be possible, we used to change nuclear submarine props without docking, mind you we did use a couple of turns of cortex to encourage the screw of the taper