Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 02-02-2010, 10:20   #1
Marine Service Provider

Join Date: Oct 2007
Boat: Endeavour 42CC
Posts: 1,182
Pitting on My Bronze MaxProp

My boat sits in fresh water. After the 2008 season (July to October), I hauled it and the prop appeared fine. After the 2009 season (April to October), the edges of the Maxprop were severely pitted, corrosion. The zinc on the prop showed minimal loss.

I sent it to PYI. The experts there think it was a sudden spike of heavy voltage. They say that low voltage doesn't go far in fresh water and the zinc was fine. The shaft zinc was perfect too.

There were no boats on either side of me the first half of the season. Both boats props are perfect after the second half of the season. I did travel for about 10 days staying in 4 marinas.

Any ideas as to what caused this rapid pitting of the prop?
__________________

__________________
gettinthere is offline   Reply With Quote
Old 02-02-2010, 10:30   #2
Registered User
 
Jon D's Avatar

Join Date: Sep 2004
Location: Ft. Lauderdale, FL currently CLODs [cruisers living on dirt]
Posts: 423
Images: 11
my bet is you had a transient in with an electrical problem. I had a similar situation where my max prop was fine for over 9 years then suddenly some pitting. There was a boat next to mine for a month or so that was not the best kept.. bet that was the problem.
__________________

__________________
Jon
S/Y Sirius
Moody 47
Jon D is offline   Reply With Quote
Old 02-02-2010, 10:35   #3
Senior Cruiser
 
senormechanico's Avatar

Cruisers Forum Supporter

Join Date: Aug 2003
Boat: Dragonfly 1000 trimaran
Posts: 5,830
While in a marina in Mexico, we had a very small bit of pitting (although nothing like yours) when a boat across from us had a welder building a cockpit arch. Several boat owners we talked to had similar damage.
__________________
Memento,homo, quia pulvis es, et in pulverem reverteris.
senormechanico is offline   Reply With Quote
Old 02-02-2010, 10:45   #4
Registered User

Join Date: Nov 2005
Location: Ohio
Posts: 2,313
Fresh water?

You should be using aluminum or magnesium anode. Zinc creates a zinc oxide that insulates the anode.

Go here for what you need. Magnesium Shaft Anodes

FYI, we have a Max Prop and use a mag anode. It's shot by seasons end on the Great Lakes.



Quote:
Originally Posted by gettinthere View Post
My boat sits in fresh water. After the 2008 season (July to October), I hauled it and the prop appeared fine. After the 2009 season (April to October), the edges of the Maxprop were severely pitted, corrosion. The zinc on the prop showed minimal loss.

I sent it to PYI. The experts there think it was a sudden spike of heavy voltage. They say that low voltage doesn't go far in fresh water and the zinc was fine. The shaft zinc was perfect too.

There were no boats on either side of me the first half of the season. Both boats props are perfect after the second half of the season. I did travel for about 10 days staying in 4 marinas.

Any ideas as to what caused this rapid pitting of the prop?
__________________
Joli is offline   Reply With Quote
Old 02-02-2010, 14:56   #5
Marine Service Provider

Join Date: Oct 2007
Boat: Endeavour 42CC
Posts: 1,182
The PYI folks feel it was a VERY big load of power all at once to create this issue.
There's been no welding near me but there have been a very few transients stayed overnight early in the year.
__________________
gettinthere is offline   Reply With Quote
Old 02-03-2010, 18:28   #6
Registered User

Join Date: Sep 2009
Location: Vancouver, BC
Boat: Ta Chiao CT34 - 34' - The Brass Monkey
Posts: 81
Could the pitting and corrosion not be a result of prop cavitation? Given that the others in the marina were unaffected and there doesn't seem to be an obvious source of charge. The imploding bubbles will actually suck the metal right off the blades and you wouldn't have noticed any appreciable loss in power.
__________________
RSMacG is offline   Reply With Quote
Old 02-03-2010, 21:32   #7
Do… or do not
 
s/v Jedi's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: in paradise
Boat: Sundeer 64
Posts: 9,198
I think the first thing you should check is your own shore power installation. I understand that it is easier on the mind to look at other possibles causes first, but that is not the best for the boat.
When other boats in your marina do not have the problem, it's very likely that the problem is on your boat.

cheers,
Nick.
__________________
s/v Jedi is offline   Reply With Quote
Old 03-03-2010, 05:21   #8
Marine Service Provider

Join Date: Oct 2007
Boat: Endeavour 42CC
Posts: 1,182
These are the things I thought of first.
But the maxprop in house experts felt that the cause was a very high voltage hit. The pitting is not on the face of the blades as would be the case from cavitation. The pitting is on the very edge. And I'm in fresh water where electricity does not flow nearly as easy as in salt. I will be checking for stray current when I get back in the water.
__________________
gettinthere is offline   Reply With Quote
Old 03-03-2010, 05:59   #9
Do… or do not
 
s/v Jedi's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: in paradise
Boat: Sundeer 64
Posts: 9,198
Okay, how does the color look like? Maybe the material has weakened?

ciao!
Nick.
__________________
s/v Jedi is offline   Reply With Quote
Old 03-03-2010, 06:24   #10
Registered User

Join Date: Feb 2010
Posts: 250
Quote:
Originally Posted by s/v Jedi View Post
I think the first thing you should check is your own shore power installation. I understand that it is easier on the mind to look at other possibles causes first, but that is not the best for the boat.
When other boats in your marina do not have the problem, it's very likely that the problem is on your boat.

cheers,
Nick.
Nick,

How do you go about checking for stray current on a boat? I had some oxydation (no pitting) on my prop after hauling out this past fall. Usually when I haul out my prop is perfectly clean, so that left me wondering whether my boat has developed a stray current problem - I just have no idea how to determine whether it does or not.
__________________
slowshoes is offline   Reply With Quote
Old 03-03-2010, 07:00   #11
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Quote:
Originally Posted by Joli View Post
Fresh water?

You should be using aluminum or magnesium anode. Zinc creates a zinc oxide that insulates the anode.

Go here for what you need. Magnesium Shaft Anodes

FYI, we have a Max Prop and use a mag anode. It's shot by seasons end on the Great Lakes.
Joli,

Where did you find a mag anode for the Max Prop? They're not shown in the referenced catalog.

Thanks,

Bill
__________________
btrayfors is offline   Reply With Quote
Old 03-03-2010, 07:04   #12
Do… or do not
 
s/v Jedi's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: in paradise
Boat: Sundeer 64
Posts: 9,198
With oxidation you mean the prop turned green?

Testing for stray currents aboard is not difficult. Just hire a marine electrician or if you are handy with multi meters, read the books and do it yourself.

Are you on shore power? If so, do you have an isolation transformer or galvanic isolator?

cheers,
Nick.
__________________
s/v Jedi is offline   Reply With Quote
Old 03-03-2010, 07:24   #13
Registered User

Join Date: Feb 2010
Posts: 250
Quote:
Originally Posted by s/v Jedi View Post
With oxidation you mean the prop turned green?

Testing for stray currents aboard is not difficult. Just hire a marine electrician or if you are handy with multi meters, read the books and do it yourself.

Are you on shore power? If so, do you have an isolation transformer or galvanic isolator?

cheers,
Nick.

No, the props not green but rather has a thin, hard white coating on it - something that has never happened before and is very hard to get off. (I didn't mention it before, but I am also in freshwater).

I am on shorepower but I have to plead ignorance on your isolation transformer/galvanic isolator question. As you have probably figured out, electricity isn't my forte, so i would probably have to hire an electrician to figure out if there is a stray current problem.

That being said, I like to at least give myself a chance at trying to figure things out for myself - do you have any recommendations on reading references that explain the steps to check for stray current?

Thanks for any info.
__________________
slowshoes is offline   Reply With Quote
Old 03-03-2010, 08:02   #14
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2006
Location: Nevada City. CA
Boat: Sceptre 41
Posts: 3,745
Images: 9
Caulsers book has a good section on testing.
__________________
Fair Winds,

Charlie

Between us there was, as I have already said somewhere, the bond of the sea. Besides holding our hearts together through long periods of separation, it had the effect of making us tolerant of each other's yarns -- and even convictions. Heart of Darkness
Joseph Conrad
Charlie is offline   Reply With Quote
Old 03-03-2010, 10:39   #15
Do… or do not
 
s/v Jedi's Avatar

Cruisers Forum Supporter

Join Date: Feb 2009
Location: in paradise
Boat: Sundeer 64
Posts: 9,198
;-) I think Charlie meant Caulder as in Nigel Caulder.

The white stuff isn't corrosion from the bronze prop because bronze corrodes green. I still wouldn't take cavitation off the list of possible problems.

Also, while reading up or getting to hire someone to inspect the electrical system aboard, disconnect your shore power. And I mean physically disconnect the cord, breaking all electrical contacts between the boat and shore. If there indeed is a severe problem like you were told, you must assure that it stops now.

Also, in your case, I would just hire a good electrician and observe him on the job. This allows you to learn as well as deal with the problem quickly. I also think you should start saving for at least a galvanic isolator or better yet an isolation transformer. Discuss it with the electrician. These devices set you back a couple of hundred dollars.

cheers,
Nick.
__________________

__________________
s/v Jedi is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Bronze Pipe Nipples Maine Sail Plumbing Systems and Fixtures 19 23-11-2009 12:22
Bronze Seawater Strainers SkiprJohn Plumbing Systems and Fixtures 18 23-10-2009 12:46
bronze cleaner steleehin Construction, Maintenance & Refit 13 07-04-2009 12:57
to MaxProp owners & gurus - need advice vacendak Propellers & Drive Systems 6 19-02-2009 15:40
WANTED: MAXPROP 20", three blade feathering avazquez Classifieds Archive 4 29-10-2007 10:42



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 16:29.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.