See a Grown Man Cry - Corroded Prop !

[DotDun]

Originally Posted by s/v Jedi

There is equipment that makes the change easy without any work needed on the 120V part of the installation. The wonder-unit is called an auto-transformer and is cheap and easy.

I already have a 5kva auto transformer, it backfeeds the 110v AC panel from European shore power. The boat is dual wired for both European 230v and US 110v - including dual receps everywhere. Two shore power cords. I never thought about using the transformer for feeding the AC units with 240/60hz....Hmm....another panel, restrap the genset for 240v....hmm. (I don't need anymore projects right now!)

[s/v Jedi]

Originally Posted by DotDun

I never thought about using the transformer for feeding the AC units with 240/60hz....Hmm....another panel, restrap the genset for 240v....hmm. (I don't need anymore projects right now!)

It'll be in your brain until you do it ;-) And it is like you say, much can be re-jumpered from 120V to 240V service incl. gensets and big electric motors like for watermakers. The things I needed to replace (anyway, they were broken) were the A/C and the inverter/charger.

An auto transformer can be used for many things. You find a whole bunch of applications in this Victron PDF: http://www.victronenergy.com/upload/...1%20-%20EN.pdf

ciao!
Nick.

[Stillraining]

240 volts scars me to death....no thanks..

[Dockhead]

Originally Posted by Stillraining

240 volts scars me to death....no thanks..

110 volts will kill you just as fast. And 220 volts (not 240); sometimes 230 volts (UK) is twice as efficient at moving energy over wires, half the amps for the same power, that much less likely to cause a fire, melt insulation, etc. I think overall it's safer.

I'm very happy our boat is 24 volts DC and 230 volts AC.

[MarkJ]

Originally Posted by Stillraining

240 volts scars me to death....no thanks..

Girl.



Nearly all civilized countries have been using it since the year dot.

Get with it and add a sparkle to your life!!!

[Dockhead]

Originally Posted by Pete7

Still good thread and for DH wind stopped its now lashing down with rain again. Tomorrows spring deck scrub is likely to be cancelled.

Pete

Sounds like normal Solent weather. Blows a gale for a while (or as you guys say, a "hooley"), then p*sses down rain for a while.

We had great weather for our cruise last week, though. It was 10 -- 12 degrees most days, wind mostly teens and 20's, a fair amount of sunshine. Rain only the last two hours of the last day.

[Dockhead]

Originally Posted by s/v Jedi

Also, I have a Victron Quattro inverter/charger. It has a feature called "Power Assist". This means that whenever it detects that I use more power than available from shore or genset even after it reduced battery charging to zero, it will add power by taking it from the batteries. For this purpose, it keeps it's inverter synchronized to the incoming power from shore or genset so that it can do this in a flash. It can add 3kW of power that way for a total of 6.6kW when I am at shore power or 9kW when I am on generator.
I can also adjust this feature to kick in at different power levels, like 2kW from shore. Handy when you blow a fuse ashore otherwise.

ciao!
Nick.

This is handy for a multitude of reasons. It allows you to run bigger loads on a smaller generator because it takes care of the startup surges. The smaller generator is better loaded and runs more efficiently. The Victron Quattro is brilliant, and one reason I don't want to spend money unnecessarily on an IT is because it would delay purchase of this fine device.

[Dockhead]

Originally Posted by Boracay

Have you considered placing anodes on the propshaft and on the hull adjacent to the propeller and evaluated the electrical systems used in your immediate vicinity?

I have a similar problem on Boracay, not as noticeable though, and have thought that it could have been caused by 1) anodes on propshaft falling off (don't ask), 2) insufficient hull anode protection adjacent to the propeller, 3) not using an appropriate primer system on the propeller, 4) the length of time the propeller had been exposed to adverse circumstances and/or 5) the possibility of stray current corrosion.

I tried getting voltage readings from the area around my boat using a zinc anode on the end of a wire. The results were interesting, but not conclusive.

Like you I fear a new propeller is in my future.

Well, could you please share your experience in more detail? It's completely relevant to the original topic of this thread.

Can you post photos of your prop?

How long was it in the water between inspections?

Zinc (prop zinc? shaft zinc?) fell off?

I am hoping that I'll be able to polish the blades of my prop and keep going. If I have to replace it, it will devastate my boat budget. I reckon it costs about $10,000.

[Boracay]

A few more details...
Originally the boat came out of the water after about 12 months in Sydney Harbour. I took the prop off to be repitched and 1) noticed that almost every anode had vanished and 2) the prop shop commented that there was evidence (the small pink "circles" that you are familiar with) of electrolysis.

I put the prop back on the boat for another year and when it came out last month there was no anode on the prop shaft and (having the prop cut down this time) the prop shop noted even more (including one dimple the size of a sixpence) corrosion. The anodes on the skeg and rudder had almost vanished as well.

The prop shop machined the propeller back to bright metal each time so any corrosion was very obvious.

This time round I put two anodes on the prop shaft and went to additional trouble to prime the prop (Internatioal PA10). I ran out of time but one of the reasons that the anode might have fallen off was that I was putting a 1 3/4" anode on a 1 7/8" shaft. (Funny how much one finds out when one measures with digital calipers).

Sorry, I took photos but no close ups of the prop.

My propeller was probably OK for another year but after that I could be looking at a new prop or a serious repair. A new prop is probably more sensible, but I'm "only" looking at $1.7 Aussie boat bucks.

[fstbttms]

Why do you assume that your anodes should still be providing protection after a year? This is not rapid depletion. Quite normal, in fact. Simply having a diver replace them at say, 6 months, seems like relatively cheap insurance and peace of mind.

[mintyspilot]

OK - dumb question of the day (because I do not know any better)

Why aren't props painted so that the metal is not in contact with the sea water. If the paint comes off, what about dipping them in epoxy resin or manufacturing them in a tough polyethylene coat over the metal body?

Surely it has been tried?

Just curious....

[s/v Jedi]

240V is the US system with two hots and a neutral. I think the EU is (should be) 230V everywhere now. The higher voltage is much better for big loads, say above 1,200W.

In shaft zincs: I lost some of those too. You can prevent that by using a thread locker on the nuts when putting them on while on the hard, or replacing the nuts with Nylock nuts when putting them on under water. You should also maintain the zincs by using a steel brush to remove the white zinc oxide so that fresh zinc is exposed to the water again. You do not have to replace zincs that still have more than 50% material as long as you check regularly so that you can replace them when needed.

When we are in a marina or at anchor for a longer period, we hang an extra zinc overboard (one of those "grouper zincs"). connect the wire to something that is grounded (electrically connected to the same metal that your permanent zinc are on). I have two shaft zincs and one on my Max prop and the grouper zinc will slow the consumption of the permanent zincs down to 1/3rd of the normal rate. You can make your own grouper zincs for free by scavenging the yard for discarded old zincs, melting them in a pot and pouring it into a moist sand mold. Drill & tap for the wire or cast it in if you're getting good at it.

ciao!
Nick.

[s/v Jedi]

Ah, zincs that don't get "eaten away"... clean the metal that you attach it to with sandpaper or my favorite: 3M metal finishing pad, which looks like a red-brown Scotchbrite pad. Works great under water too. A shaft-zinc must fit around the shaft perfectly. I often need a mallet to convince it to fit. When on the hard you can use a multimeter on Ohm (resistance) setting for testing good contact. Remove labels and brush until shiny with a steel brush (yes for new zincs too).

If you have good contact, brushed clean anodes and they are still not "eaten away" you are fine. It might change though when you move the boat or something else around her changes so keep checking them every 6 months. When you have corrosion on the prop but the zinc is still okay there is something wrong, probably bad electrical contact between the zinc and the prop.

ciao!
Nick.

[fstbttms]

Originally Posted by s/v Jedi

When you have corrosion on the prop but the zinc is still okay there is something wrong, probably bad electrical contact between the zinc and the prop.

Not necessarily. Case in point:
Last summer a customer of mine with a Jeanneau SunFast 35 and a folding prop suddenly began experiencing very rapid and severe corrosion on the prop. Here are some pix:



The corrsion visible in these pix occurred in about a month's time. The zinc did not display undue depletion. I added a second zinc as increased protection, but the problem continued throughout the summer. I was diving the boat frequently, it being the height of the race season, and would wire brush the prop as clean as possible. Each time I came back however, the prop looked like this. I advised the client from the outset that he should have a marine electrician go through the boat's systems. The client (inexplicably, having seen the pictures) chose not to do this.

After several months, the bilge pump ceased working and the owner had it replaced. The instant the new bilge pump was installed, the corrosion issue ceased. Turns out the wires powering the old bilge pump were missing some insulation and were bleeding current into the bilge.

Unfortunately, the damage was done. Several months ago, the prop came off the boat at some point during a day sail and the owner had to buy a brand new one.

In any event, rapid-onset corrosion is not necessarily due to a poor anode bond. If you are truly concerned, have an electrician take a look. Could save your prop and/or the boat.

[Pete7]

Originally Posted by mintyspilot

OK - dumb question of the day (because I do not know any better)

Why aren't props painted so that the metal is not in contact with the sea water. If the paint comes off, what about dipping them in epoxy resin or manufacturing them in a tough polyethylene coat over the metal body?

Surely it has been tried?

Just curious....

I always paint mine. Never had to much sucess when we had an aliminium prop as paint just fell off but now we have a yacht and bronze prop a thin coat of Premicon and another of micron, it seems to last a year.

Pete