Newport 30 Thru-hull replacement - SailNet Community
 
LinkBack Thread Tools
post #1 of 7 Old 03-28-2007 Thread Starter
Junior Member
 
Join Date: Mar 2007
Posts: 7
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Newport 30 Thru-hull replacement

Anyone replaced the TH's on a Newport 30 (MKIII)? Mine are the originals from '82 and although I replaced the old plastic valves, I think it's time to replace the TH's themselves. Looks like they're embedded in the hull and then faired over with a layer of gel, so it may be more work than I want... any tips appreciated!

-Dave
dasnider is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #2 of 7 Old 03-29-2007
STARBOARD!!
 
KeelHaulin's Avatar
 
Join Date: Mar 2006
Posts: 1,662
Thanks: 0
Thanked 2 Times in 2 Posts
Rep Power: 11
   
Dave-

Unless the backing blocks on the interior side are rotten/leaking or heavily corroded I would suggest leaving them alone. Another way to check for corrosion is grinding back the surface of the thru hull on the exterior. If it is bright and shiny with no red spots then it is still sound. The red color indicates loss of lead due to galvanic corrosion.

The reason I suggest leaving them as-is is because the thru-hulls on my N-41 are in excellent condition. When we did the bottom job last year I removed one of the thru-hulls in the stern (the engine raw water intake) and it was in great shape with no signs of corrosion. The only reason I did not put it back in is because I damaged the threads while removing it. The bronze thru-hull I replaced it with was much lighter in construction. The OD of the flange was small and it did not fit perfectly to the molded recess to the hull (there is gelcoat beneath the fitting). So on the forward thru-hulls I ground back the old fairing compund painted the surfaces with epoxy and then re-faired them with thickened epoxy.

JMHO/HTH...
KeelHaulin is offline  
Quote Quick Reply Share with Facebook
post #3 of 7 Old 03-30-2007
Junior Member
 
Join Date: Dec 2003
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
The marina put on a class on bonding of thru hulls. He told me that the older boats used a superior type of bronze that is highly resistant to corrosion. My N-30III shows no signs of corrosion or color change. I bonded them anyway to the cutlass bearing zink, 750 Ma of current flowing from thru hulls to zink
Gorey is offline  
Quote Quick Reply Share with Facebook
post #4 of 7 Old 04-01-2007
STARBOARD!!
 
KeelHaulin's Avatar
 
Join Date: Mar 2006
Posts: 1,662
Thanks: 0
Thanked 2 Times in 2 Posts
Rep Power: 11
   
Quote:
Originally Posted by Gorey
The marina put on a class on bonding of thru hulls. He told me that the older boats used a superior type of bronze that is highly resistant to corrosion.
Interesting... I also noticed the thickness was greater; the old fitting weighed at least 1/3 more than the new one. Could you explain why you would want to bond all of your thru-hulls to a zinc? I thought that any isolated thru-hull (with no direct connection to the electrical; like cockpit/sink drains) should be left without a bonding wire to keep it electrically isolated.
KeelHaulin is offline  
Quote Quick Reply Share with Facebook
post #5 of 7 Old 04-02-2007
Junior Member
 
Join Date: Dec 2003
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Quote:
Originally Posted by KeelHaulin
Interesting... I also noticed the thickness was greater; the old fitting weighed at least 1/3 more than the new one. Could you explain why you would want to bond all of your thru-hulls to a zinc? I thought that any isolated thru-hull (with no direct connection to the electrical; like cockpit/sink drains) should be left without a bonding wire to keep it electrically isolated.
The bonding wire is like a belt and suspenders. On newer boats the thru hull's are bonded. My boat was made in 1985 and the thru hussl look good. I did replace the Marlon plastic valves with brass.
Gorey is offline  
Quote Quick Reply Share with Facebook
post #6 of 7 Old 04-07-2007
STARBOARD!!
 
KeelHaulin's Avatar
 
Join Date: Mar 2006
Posts: 1,662
Thanks: 0
Thanked 2 Times in 2 Posts
Rep Power: 11
   
Quote:
Originally Posted by Gorey
The bonding wire is like a belt and suspenders. On newer boats the thru hull's are bonded. My boat was made in 1985 and the thru hussl look good. I did replace the Marlon plastic valves with brass.
I would not assume that you need bonding on all thru-hulls; sometimes if there is a grounding problem you can create more problems if the thru-hulls are attached together and have a pathway to the electrical loop. If your thru-hulls are sound now and they are 20+ years old I would not add bonding to prevent them from suffering galvanic corrosion. If they had been corroding there would have been evidence of it by now.
KeelHaulin is offline  
Quote Quick Reply Share with Facebook
post #7 of 7 Old 06-16-2007 Thread Starter
Junior Member
 
Join Date: Mar 2007
Posts: 7
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Thanks for all the recommendations. I had wire-brushed away the corrosion from a couple of the THs when I bought the boat 3 years ago and it looked a bit pinkish, so I was planning on replacing them. However based on the feedback to this thread I got in there with a file and really got down to bare metal, and it's bright bronze - so I guess I'm OK! Seems there's just a surface layer of reddish corrosion.

A couple of them are weeping so while I had her out I cleaned out between the TH and the gelcoat and sealed it up with epoxy, so hopefully that'll fix the problem.

Appreciate the advice,

-Dave
dasnider is offline  
Quote Quick Reply Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Thru Hull Replacement Stormer_2003 Gear & Maintenance 1 09-13-2004 11:22 AM
Thru Hull Replacement Stormer Gear & Maintenance 4 08-03-2004 08:21 AM
Spring Hull Cleaning Tom Wood Gear and Maintenance Articles 0 04-05-2004 08:00 PM
Hull Speed Demystified Steve Colgate Learning to Sail Articles 0 06-10-2000 08:00 PM
Hull Speed Demystified Steve Colgate Buying a Boat Articles 0 06-10-2000 08:00 PM

Posting Rules  
You may post new threads
You may 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 On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome