Fizzing Prop or is it just Old & Knackered?

[Sishoe]

Being new to the frighteningly simple shaft & rudder world, could I ask for comments of the rather knackered port prop in the photo link below.

Bit of background, when the boat was surveyed back in the summer, it was picked up that the port prop was showing signs of electrolysis/pinking, and the starboard prop had some light damage. Both were sent to a local prop shop, one for repair and the other to be measured for the manufacture of a replacement.
I had all the anodes replaced and the boat was relaunched prior to handover to me.
Roll the clock forward 3 months and the boat is now out the water again, and had its replacement prop fitted. The pictures on the link below are from the current lift prior to the prop being replaced.
All the anodes I fitted back in May have worn equally, the shaft, P-bracket and rudder on the port side look fine, only the prop appears to have continued to deteriorate.
My question is could this just be an old worn out prop that is naturally de-zincing at the end of its life (the starboard prop possibly having already been replaced) or does it look like I have a problem? would not everything thing on the port side be effected if I had a continuity problem on that side (the continuity is being checked, I'm yet to know the result).
The boat is 8 years old.

https://1drv.ms/f/s!AoMBqVrTEKbpqQGiy-pF6r9-gGdg

 

[burgundyben]

What material is it?

Props usually bronze, so no zinc to leach away.

I reckon that's an anode bonding failure. You should get max 0.3 ohms on a mulitmeter between prop and anode.

 

[CLB]

That looks quite bad. Have you ruled out electrolytic corrosion caused by stray currents?

 

[andrewbarker]

Unless they're manganese bronze which can be up to 40% zinc

What material is it?

Props usually bronze, so no zinc to leach away.

I reckon that's an anode bonding failure. You should get max 0.3 ohms on a mulitmeter between prop and anode.

 

[Sishoe]

What material is it?

Props usually bronze, so no zinc to leach away.

I reckon that's an anode bonding failure. You should get max 0.3 ohms on a mulitmeter between prop and anode.

Thanks, So can bronze props potentially last forever, if not effected at some point by electrolytic corrosion? The continuity is being checked today so will know soon.

That looks quite bad. Have you ruled out electrolytic corrosion caused by stray currents?

I'm going to check the galvanic isolator, that's if it has one, do Fairline fit them? There is also a big box of electronics that control the shore power supplies, and is located in the engine room directly above where the damaged prop is, it has been mentioned that this might have something to do with it.

Any ideas why only the prop & prop nut appears to be effected and not the P - bracket/shaft?

 

[Sishoe]

Unless they're manganese bronze which can be up to 40% zinc

Checking the sales lit, it does specify Manganese Bronze props.
https://1drv.ms/b/s!AoMBqVrTEKbpqAlwGNi1DaV86Cq3

 

[Tranona]

Thanks, So can bronze props potentially last forever, if not effected at some point by electrolytic corrosion? The continuity is being checked today so will know soon.



I'm going to check the galvanic isolator, that's if it has one, do Fairline fit them? There is also a big box of electronics that control the shore power supplies, and is located in the engine room directly above where the damaged prop is, it has been mentioned that this might have something to do with it.

Any ideas why only the prop & prop nut appears to be effected and not the P - bracket/shaft?

Highly unlikely it will be bronze. That word covers a whole variety of alloys but props are normally made now of managanese "bronze" which has zinc in it. Hence the need for anodes. Suspect the bond has broken on the port side if you are relying on a hull anode bonded to the shaft. As suggested it needs a check on continuity between the anode and the prop.

The p bracket is not connected to the prop and may well be bonded to the anode although P brackets rarely suffer from dezincification because unlike props are not connected to other metals such as the prop to shaft.

 

[omega2]

Is there a bridge across the r&d coupling? and that nibbling looks like you have been ploughing? also that amount of growth in three months? you should plant strawberries. LOL

Talk to Paul Williams, www.clementsmarine.co.uk he will put you straight.

 

[kashurst]

You may also have carbon brush contacts on the shaft. These can stick so not making good contact to the shaft and you loose galvanic protection. Also they have a fine flexible wire from the contact arm to the support. These can corrode away too.
Prop looks knackered though. Check it all out with an ohm meter.

 

[Bandit]

Props are bronze and de-zincificaton will occur if they are not protected.

A protected bronze prop will last pretty well forever if it is correctly protected.

You need to get props, shafts, p brackets, rudders, and all skin fittings initially checked for connectivity to anodes and work out what is connected to what.

Then check all internal anode wiring on the inside for condition and whether it is connected properly.

Check shaft brushes and connection accross R&D as already advised.

Then check boat with DC on and various kit on to see if there is an earth on DC.

Then check with AC on and see if there is a leak.

 

[Tranona]

Props are bronze and de-zincificaton will occur if they are not protected.

A protected bronze prop will last pretty well forever if it is correctly protected.

You need to get props, shafts, p brackets, rudders, and all skin fittings initially checked for connectivity to anodes

I can understand props and shafts and possibly rudders because they are two metals together, possibly p brackets if they are bolted with stainless bolts, but there is no need to bond skin fittings to anodes as they are all one metal and if of the common DZR or bronze material do not need any protection.

 

[Portofino]

What type of prop anodes ?
Should they be hex cone bolted on via the threaded hole in the prop retaining bolt visible in your pics in post #1 ?
View attachment 66750

 

[volvopaul]

Something seriously wrong with either your shore power set up looking at how badly corroded the prop is on a boat that young in age .

 

[Sishoe]

What type of prop anodes ?
Should they be hex cone bolted on via the threaded hole in the prop retaining bolt visible in your pics in post #1 ?
View attachment 66750

I Can’t see how a prop anode could be attached in this way to my setup, I don’t have a tapped hole in the end of the shaft, or am I missing something?

I’ve heard this afternoon from the engineers who fitted the new prop that they found a continuity issue, which was tracked down to a loose wire to the anode, although I’m yet to speak to the actual engineer who checked it. I think i’ll need to see both sides retested with my own eyes before relaunching though.

 

[gordmac]

Worth fitting shaft anodes if you don't have them?

 

[Bandit]

I can understand props and shafts and possibly rudders because they are two metals together, possibly p brackets if they are bolted with stainless bolts, but there is no need to bond skin fittings to anodes as they are all one metal and if of the common DZR or bronze material do not need any protection.

I don't know what the OP's boat is.

Some manufacturers fitted brass skin fittings and ball valves , you would be surprised which manufacturers did fit brass.

I dare say some may be a mixture also of brass skin fittings and DZR valves or vice versa.

At eight years old either remove all skin fittings and valves inspect and replace only if perfect or replace all with newDZR, the labour is the same, personally I would replace with new.

There are two schools of thought if you know its DZR ( but do you really with a second hand boat) some don't bond, I work on the basis of bond and be sure.

Looking at the boat it had no prop cone anodes or shaft anodes.

Its worth getting the continuity checked on the boat at least annually.

Also make sure you use serrated washers for anodes to ensure electrical connection outside the hull.

 

[Tranona]

I don't know what the OP's boat is.

Some manufacturers fitted brass skin fittings and ball valves , you would be surprised which manufacturers did fit brass.

I dare say some may be a mixture also of brass skin fittings and DZR valves or vice versa.

At eight years old either remove all skin fittings and valves inspect and replace only if perfect or replace all with newDZR, the labour is the same, personally I would replace with new.

There are two schools of thought if you know its DZR ( but do you really with a second hand boat) some don't bond, I work on the basis of bond and be sure.

Looking at the boat it had no prop cone anodes or shaft anodes.

Its worth getting the continuity checked on the boat at least annually.

Also make sure you use serrated washers for anodes to ensure electrical connection outside the hull.

It is a Fairline as stated in post#5 so unlikely to have brass fittings. However connecting to an anode won't stop brass fittings from dezincifying eventually (and not all do anyway).

As the problem is only on one side of the boat and only affects the prop, the cause is almost certainly defective bonding between the shaft/prop assembly and the anode.

 

[Bandit]

It is a Fairline as stated in post#5 so unlikely to have brass fittings. However connecting to an anode won't stop brass fittings from dezincifying eventually (and not all do anyway).

As the problem is only on one side of the boat and only affects the prop, the cause is almost certainly defective bonding between the shaft/prop assembly and the anode.

You would be surprised which manufacturers fitted brass fittings at one time.

I never said that brass skin fittings and valves being bonded is the answer, Brass skin fittings and valves have no place on a boat under the waterline.

I agree that the " the cause is almost certainly defective bonding between the shaft/prop assembly and the anode".

The whole boat needs checking over for continuity anyway ( not just the significant problem addressed) and condition of anode wiring inside the hull needs verification, the OP did not know he had a problem till the boat came out of the water.