Martec Prop Cotter Pins - Page 2 - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
  #11  
Old 04-04-2009
Sea Slacker
 
Join Date: Jan 2007
Posts: 1,789
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
brak is on a distinguished road
Quote:
Originally Posted by Fstbttms View Post
This doesn't even make sense.
why not?
Reply With Quote Share with Facebook
  #12  
Old 04-04-2009
Fstbttms's Avatar
I don't discuss my member
 
Join Date: Feb 2003
Location: Under a boat, in a marina, in the San Francisco Bay
Posts: 2,082
Thanks: 4
Thanked 18 Times in 18 Posts
Rep Power: 12
Fstbttms will become famous soon enough
Quote:
Originally Posted by brak View Post
why not?
1.- The size of the shaft relative to the pins and its position relative to the prop and boat do not affect whether or not, or to what extent, electrolytic corrosion will occur.

2.-
Quote:
Originally Posted by brak View Post
Pins are small and they are between prop and water...
Quote:
Originally Posted by brak View Post
so since stainless is less noble than bronze, pins will act as sacrificial anodes and may dissolve relatively quickly.
The first part of this sentence (besides being completely irrelevant) has absolutely no relation to the second part.

3.- The pins are made of monel because monel is galvanically closer to bronze than stainless is (as you correctly pointed out). However, this is to prevent galvanic corrosion, not electrolytic corrosion.
Reply With Quote Share with Facebook
  #13  
Old 04-04-2009
Sea Slacker
 
Join Date: Jan 2007
Posts: 1,789
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 8
brak is on a distinguished road
[QUOTE=Fstbttms;470918]1.- The size of the shaft relative to the pins and its position relative to the prop and boat do not affect whether or not, or to what extent, electrolytic corrosion will occur.

2.-

The first part of this sentence (besides being completely irrelevant) has absolutely no relation to the second part.

Quote:
3.- The pins are made of monel because monel is galvanically closer to bronze than stainless is (as you correctly pointed out). However, this is to prevent galvanic corrosion, not electrolytic corrosion.
The two are intimately related, in particular when we are talking about prop shaft and anything attached to it. Practically all diesel engines are electrical ground for their alternators and as such, shaft/prop etc act as a ground path to the water (unless specifically disconnected through a coupler).

Boat ground is higher in potential than water and it does create current. Galvanic and electrolytic corrosion have essentially same mechanism - difference in potential created in one case by external source of electric potential and in another by different pontential between dissimilar metals in electrolyte.
Generally speaking simple difference of potential between stainless and bronze is not sufficient to create significant corrosion, but the ground current from the boat helps this process quite a bit.
Reply With Quote Share with Facebook
  #14  
Old 04-06-2009
rperret's Avatar
Senior Member
 
Join Date: Apr 2003
Location: Western Long Island Sound
Posts: 221
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 12
rperret is on a distinguished road
gotcha...thanks.

Quote:
Originally Posted by brak View Post
Shaft is big, and it is also towards the boat from the prop. So the electricity flow is from shaft to prop to water. This prevents much corrosion occuring at shaft. Pins are small and they are between prop and water, so since stainless is less noble than bronze, pins will act as sacrificial anodes and may dissolve relatively quickly.
__________________
The beat goes on, the beat goes on...

The grocery stores the super mart, uh huh
Little girls still break their hearts, uh huh
And men still keep on marching off to war
Electrically they keep a baseball score

The beat goes on, the beat goes on...
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
martec feathering 2 blade prop j34035 Gear & Maintenance 2 03-13-2009 08:46 PM
martec prop refurb dvpamenter Gear & Maintenance 2 01-13-2008 02:31 PM
Changing prop underwater trantor12020 Gear & Maintenance 16 03-03-2007 12:02 PM
Choosing the Right Propeller Sue & Larry Gear and Maintenance Articles 0 02-04-2003 07:00 PM
Martec Geared Folding Prop rtcooke Gear & Maintenance 1 05-13-2001 06:05 AM


All times are GMT -4. The time now is 04:46 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.