Changing a propeller in water

[gordontytler]

When I did my RYA insure helmsman I was told to carry a sharp knife and a spare propeller. I have used the sharp knife to cut a rope wrapped round the prop shaft. Now it is time to use the spare propellor.

The two propellors rotate in opposite directions so should I expect the thread on the shafts to also be in opposite directions or is the key slot sufficient?

Any advice on removing and fitting a propeller while in water appreciated. Also, where to buy a propeller and a large spanner.

thanks

 

[MagicalArmchair]

This made some interesting viewing for me when I was changing my propeller OUT of the water:

 

[vyv_cox]

Cannot advise on the thread, although I would have expected both to be right hand. So far as removing one in the water is concerned, there are many threads on this site listing the problems they have removing props in the yard! I think you would be extremely lucky.

 

[sailaboutvic]

I would think twice before doing it in the water , I change my zine underwater and that's a big enough job , trying to use a pulley underwater Mmmm any way good luck . But in the end it may cost you a lot more then a lift out .

 

[duncan99210]

Never changed a shaft mounted prop but I've removed the Brunton Autoprop from the Saildrive several times now. It is not an easy task! The biggest hazard is dropping bits after removal or as you're fitting them. I hang a bucket from the Saildrive under the prop to hold tools and bits as well as catching them if dropped. The first time I did the job, I used a thigh pouch for tools and bits but found it very difficult to tell one tool from another, let alone which Allen bolt was which.... The bucket make life easier, as you can look into it to find the right tool/bit.

The other problem is buoyancy control when you finally get the prop off: you've been neutrally buoyant, then you slide the prop off and suddenly you're a good few kilos heavier and you've got your hands full of prop. Cue fast descent. I now get to the point of removing the prop, put some air into the BCD so as to bang my head on the hull and only then remove the prop.

Finally, currents can play their complicating part. I had to remove the prop at anchor, the wind got up whilst I was underwater and the boat started the usual swinging. That just made everything that little bit harder as I had to hang on to the boat as well as trying to remove the prop...

I'd not like to tackle the job on a taper fit prop where I'd need to use a puller to remove it. However, I can see how to do it but it would really need two divers to ease the task along. I mean, it bad enough getting a puller set up on land where you've got two hands to to the job.

 

[Davegriff]

My boat has a saildrive so relatively easy to change, but I still wouldn't want to tackle it underwater unless really desperate.

 

[RichardS]

I removed both my props from my saildrives on the hard. One came off OK with a bit of brute force and, in theory, I could have done it underwater. The other needed an angle grinder to grind off the spinner and then I had to use a gas torch to loosen up the remnants because the thread was covered with Loctite. Underwater? I don't think so.

Richard

 

[GrahamHR]

I've changed some DPS duo props when afloat; very easy as long as you have the special tool for the forward one. Both RH threads with nylok type nuts.

 

[30boat]

I've removed fixed props under water and then put them back on and also whole shafts.Once after losing my fixed prop I replaced it underwater with a folding one that didn't have grubscrews but split pins instead.Very fiddly but I didn't lose any bits.The main problem is bits disapearing into the depths so tie everything up and as said hang a bucket underneath.It can be complicated but it's feasible if you can hold your breath well.

 

[CheekyFellow]

Changing a propeller on the boat im on is a mega undertaking that I would only attempt in depths of 5m just or a little less (prop weighes ooo 30kg+

 

[BobnLesley]

I once changed the two-bladed fixed prop on an Albin Vega underwater - just a snorkel too, no bottled-air - and found it quite easy/straightforward, though the Vega prop's relatively small, positioned astern of the rudder (I wouldn't like do our current one) and it had been off only about 4 months earlier, so I knew the end-nut would come off cleanly. But where's the OP located? I was in Sardinia, but if I'd been in the UK I would've simply dried-out at low tide.

 

[Bandit]

Assuming the boat in the photos is the one in question ie twin screw motor boat 30 to 40 ft and assuming the props were properly fitted previously it will be extremely difficult if not impossible for an amateur diver (with air bottles), for a couple of trained divers used to this kind of work its do able assuming the prop comes off with a puller. If you need to apply heat the boat will need to come out of the water.

If the prop has to be changed due to damage I would do it out of the water so i could inspect all associated areas for damage.

However to do the job properly take it out of the water.

Replacement props to suit are very rarely available off the shelf and are normally available only to order.

Unless the new prop and key has been matched to the shaft before and ground to suit I would do the job properly ashore.

 

[Elessar]

Assuming the boat in the photos is the one in question ie twin screw motor boat 30 to 40 ft and assuming the props were properly fitted previously it will be extremely difficult if not impossible for an amateur diver (with air bottles), for a couple of trained divers used to this kind of work its do able assuming the prop comes off with a puller. If you need to apply heat the boat will need to come out of the water.

If the prop has to be changed due to damage I would do it out of the water so i could inspect all associated areas for damage.

However to do the job properly take it out of the water.

Replacement props to suit are very rarely available off the shelf and are normally available only to order.

Unless the new prop and key has been matched to the shaft before and ground to suit I would do the job properly ashore.

agree wth this and much of the advice thusfar.

i recently had a lift and hold, removed the props, had then refurbed and refitted them in the water. Even so, as has been stated, a new prop should be ground in this isn't possible in the water. Refitting was, without doubt, a 2 person in the water plus one on the shore job.

Removal in the water? I have tried but not succeeded.

Other OP Qs.
Both RH thread.
Norris's or steel developments.

 

[bikedaft]

Done it once - but the prop was loose on the shaft as the key had split, so knew it would come off...

Low tide/drying out is always going to be easier