Reply
 
Thread Tools Search this Thread Display Modes
 
Old 01-31-2017, 12:21 PM   #1
Senior Member
 
Oldersalt's Avatar
 
City: San francisco
Country: USA
Vessel Name: Pacific Star
Vessel Model: 1990 Grand Banks 32 #834
Join Date: Jun 2016
Posts: 160
GB 32 shaft problem...

Just had my new-to-me 1990 Grand Banks 32 hauled. Prop had to be replaced due to electrolysis corrosion. The yard said the 1 1/2-inch shaft has "unknown" threads which would not fit any known zinc! Boat is now back in the water with no prop protection so I need to move quickly to solve this problem.

Anybody have any experience with a GB shaft with non-standard threads??

The yard said I should install a brush on the shaft, connected to the transom zinc, but those are prone to failure. I would rather find a better solution.

I'm considering having a diver temporarily remove one of the existing shaft nuts, determining exactly what the thread is, and having a new nut tapped to the right threads. The new nut would be sized correctly to accept a shaft zinc, of course.

Any actual experience, or thoughts, on the best way to handle this?

Thanks in advance.
Oldersalt
__________________
Advertisement

Oldersalt is offline   Reply With Quote
Old 01-31-2017, 12:30 PM   #2
Guru
 
Heron's Avatar
 
City: Cypress Landing Marina (NC)
Country: USA
Vessel Name: Heron (2)
Vessel Model: '88 Cape Dory 28 Flybridge #115
Join Date: Nov 2014
Posts: 1,303
My Zincs clamp to the shaft just forward of the prop. Standard 1.5" and $15 or so available anywhere. Not enough room for that style?? I would have thought the yard would have figured that out..

There is often insufficient threading for the style you describe....Depending on the shaft design of course.

__________________

__________________
Steve
Heron is offline   Reply With Quote
Old 01-31-2017, 12:45 PM   #3
Guru
 
Giggitoni's Avatar
 
City: Vallejo, California
Country: United States
Vessel Name: Mahalo Moi
Vessel Model: 1986 Grand Banks 42 Classic
Join Date: Jun 2008
Posts: 1,766
We've had brushes on the shafts in the bilge for nine years. No problem so far. As far as I can determine, with a set up like ours, there is no need for external shaft zincs. We have plenty of room between the transmissions and stuffing boxes.
__________________
Ray
"Mahalo Moi"
1986 GB-42 Classic
ΜΟΛΩΝ ΛΑβΕ
Giggitoni is offline   Reply With Quote
Old 01-31-2017, 01:20 PM   #4
Guru
 
Xsbank's Avatar
 
City: Pender Harbour, BC
Country: Canada
Vessel Name: Gwaii Haanas
Vessel Model: Custom Aluminum 52
Join Date: Sep 2013
Posts: 3,245
My 32 had a shaft brush that connected to a bus bar which was connected to the transom zinc, as well as a shaft zinc. It had a galvanic isolator in the circuit and no damage from galvanic corrosion when I owned her.

Stainless steel is a VERY poor conductor so you need to constantly check that the brushes are making continuity with the shaft. A good digital meter will tell you that.

Grand Banks used copper straps to bond everything and many of mine were corroded or not possible to tell if they were effective so I replaced all of it with 8 gauge green tinned wire and terminated everything at bus bars so no stacking of connections.
__________________
Don't believe everything that you think.
What are we offended about today?
Xsbank is offline   Reply With Quote
Old 01-31-2017, 01:21 PM   #5
Guru
 
City: Fairport
Country: United States
Join Date: Jan 2017
Posts: 1,690
Quote:
Originally Posted by Oldersalt View Post

The yard said I should install a brush on the shaft, connected to the transom zinc, but those are prone to failure. I would rather find a better solution.


Any actual experience, or thoughts, on the best way to handle this?

Thanks in advance.
Oldersalt
Hi; here is my actual experience. I have spent a lot of time at boat yards, and what I see is a lot of shafts that loose their zincs before they get hauled. So, lots of shaft zinc "failures".
I went to shaft brushes and never looked back. Being a southern boater, I didn't have to worry with pre-haulout zincs getting loose on the shaft or even rotting off. I installed the shaft brushes myself, and bonded them to the ships ground, which did include a transom zinc. It took care of the shafts, and props. The rudders are not directly bonded, so I still used zincs on those. I never did wear out a shaft brush. Went maybe 10 years or so, and that was on a high speed shaft, turning about 2000 rpm at cruise.
diver dave is offline   Reply With Quote
Old 01-31-2017, 01:47 PM   #6
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 16,094
I used an overboard zinc on a wire that had a clamp on the end. Like an alligator clamp and attached it to the prop shaft while anchored or underway. Worked well.

Now I use a zinc nut. You won't find a blank zinc nut to machine in a store I don't think. Where do you plan on finding a blank nut? Could make square nuts fairly easily from bar stock. I'd go w the diver to remove a nut plan.

Actually a better long term idea is to take your shaft out and get a "shaft saver" (orange) and cut/machine your prop shaft shorter on the prop end the same length of the shaft saver. Of course you'd cut the threads on the new shaft end to match whatever thread you wanted. A common shaft nut thread would be best.
__________________
Eric

North Western Washington State USA
Nomad Willy is offline   Reply With Quote
Old 01-31-2017, 03:37 PM   #7
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 5,359
Sometimes the Aisian and Euro shafts come with goofball threads and tapers. Can be a PITA.

Shaft brush should do fine. Just do a good job and get a dedicated high quality lead to the transom zinc.
Ski in NC is offline   Reply With Quote
Old 02-01-2017, 01:49 PM   #8
Guru
 
Aquabelle's Avatar
 
City: sydney
Country: australia
Vessel Name: Aquabelle
Vessel Model: Ocean Alexander Flushdeck
Join Date: Jun 2012
Posts: 907
Quote:
Originally Posted by Oldersalt View Post

The yard said I should install a brush on the shaft, connected to the transom zinc, but those are prone to failure. I would rather find a better solution.

Oldersalt
I don't know why you would think shaft brushes (or straps) are "prone to failure"; my experience is that they are not. And they are easily inspected, unlike zincs which are not seen until the boat is hauled or dived. I think you should take the yard's advice ( & I see most of the posts above are +ve on shaft brushes too)
Aquabelle is offline   Reply With Quote
Old 02-01-2017, 02:26 PM   #9
Guru
 
Lou_tribal's Avatar
 
City: Quebec
Country: Canada
Vessel Name: Bleuvet
Vessel Model: Custom Built
Join Date: Jan 2016
Posts: 3,516
I read that shaft brush can reduce "singing" noise cause by shaft rotation, is that true?
I find that these brush are a nice solution, how hard are they to install? Any advice?
Lou_tribal is offline   Reply With Quote
Old 02-01-2017, 02:55 PM   #10
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 16,094
Reduce singing? I doubt it.

After this thread I may go back to the brush. My bullet shaped prop zinc is usually wasted when I haul out. And I hate putting it on and taking it off. I still have the double nuts.

For the OP (at your next haulout) a short section of shaft probably available at ant machine shop that does shafts could cost next to nothing and a coupling. Figure out where to make the splice and have at it. A splice/coupling would probably be best close to the trans flange. I like the tubular two piece coupling.
__________________
Eric

North Western Washington State USA
Nomad Willy is offline   Reply With Quote
Old 02-01-2017, 03:28 PM   #11
Guru
 
Giggitoni's Avatar
 
City: Vallejo, California
Country: United States
Vessel Name: Mahalo Moi
Vessel Model: 1986 Grand Banks 42 Classic
Join Date: Jun 2008
Posts: 1,766
OP, Oldersalt,

I notice that you're in the San Francisco Bay Area. Contact Malcolm Morgan. He is with Johnson Hicks Marine Electronics in Sausalito.

Malcolm is, in my opinion, the most knowledgeable person on the planet regarding marine electrolysis. He will recommend shaft brushes and a good galvanic isolator for your system.

His information is:

Malcolm Morgan
Johnson Hicks Marine Electronics
298 Harbor Drive
Sausalito, CA 94965
(415) 331-3166
__________________
Ray
"Mahalo Moi"
1986 GB-42 Classic
ΜΟΛΩΝ ΛΑβΕ
Giggitoni is offline   Reply With Quote
Old 02-01-2017, 03:30 PM   #12
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 5,359
Willy- if you do a shaft brush, keep the bullet zinc, it will probably last four times as long. And it will take over if shaft brush circuit fails. Which they do.
Ski in NC is offline   Reply With Quote
Old 02-01-2017, 04:44 PM   #13
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,436
Quote:
Originally Posted by Lou_tribal View Post
I read that shaft brush can reduce "singing" noise cause by shaft rotation, is that true?
I find that these brush are a nice solution, how hard are they to install? Any advice?
Where did you read that?
Capt.Bill11 is offline   Reply With Quote
Old 02-01-2017, 04:47 PM   #14
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,436
So it took 27 years for the prop to go bad?

Not sure you have much to worry about.
Capt.Bill11 is offline   Reply With Quote
Old 02-01-2017, 04:58 PM   #15
Guru
 
Lou_tribal's Avatar
 
City: Quebec
Country: Canada
Vessel Name: Bleuvet
Vessel Model: Custom Built
Join Date: Jan 2016
Posts: 3,516
Quote:
Originally Posted by Capt.Bill11 View Post
Where did you read that?
From promariner shaft brush description:

Can eliminate radio frequency noise from rotating shaft.

But now I think I misread it and I guess they are not talking about singing noise but noise on RF.
Lou_tribal is offline   Reply With Quote
Old 02-01-2017, 10:42 PM   #16
Guru
 
C lectric's Avatar
 
City: B.C.
Country: Canada
Vessel Name: Island Pride
Vessel Model: xxxx
Join Date: Oct 2007
Posts: 2,476
I installed a shaft brush 8-10 years ago and no failure yet. Of course I do check a couple times a year.
C lectric is offline   Reply With Quote
Old 02-01-2017, 11:38 PM   #17
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 16,094
Quote:
Originally Posted by Ski in NC View Post
Willy- if you do a shaft brush, keep the bullet zinc, it will probably last four times as long. And it will take over if shaft brush circuit fails. Which they do.
Great thought Ski,
But then I'd still need to fight w the zinc nut. The adjustment point always seems to be between the slots. Spoze I could go with the not so tight slot and use blue lock tight. Don't like taking the hammer to the shaft to get the prop off. I use a torch and just the puller. Never have to use the hammer.
But now I know the drill and it's not as much stress as it used to be.
Thanks
__________________
Eric

North Western Washington State USA
Nomad Willy is offline   Reply With Quote
Old 02-02-2017, 09:51 AM   #18
Veteran Member
 
Busterbrown's Avatar
 
City: Corona
Country: USA
Vessel Name: SCRAMBLER
Vessel Model: 1974 Grand Banks 32 #536
Join Date: Jul 2013
Posts: 58
Oldersalt my 74 has a whitworth thread and nuts on the shaft I also have the shaft strapped. I could not find a shaft nut with whitworth threads so I used the size F shaft nut. Propeller Nut With Zinc Anode - Specifications It will be a little loose going on because of thread pitch. I used the smaller original prop nut first. Hope that helps and if anyone knows where to get a 1 1/2 whitworth threaded zinc prop nut let us know?
Busterbrown is offline   Reply With Quote
Old 02-02-2017, 01:22 PM   #19
Guru
 
Xsbank's Avatar
 
City: Pender Harbour, BC
Country: Canada
Vessel Name: Gwaii Haanas
Vessel Model: Custom Aluminum 52
Join Date: Sep 2013
Posts: 3,245
I think you guys are vastly over-analyzing this. Use a shaft brush. They are not cheap but they last for years, which is more than you can say for prop zincs. You don't need a prop zinc. You could add a belt to your suspenders and use a shaft zinc but that is not essential either. Just keep the transom zinc free of growth and be very sure the electrical connections to the very poor-conducting stainless bolts is as good as you can get. I had zero galvanic corrosion with my 'glass 32.
__________________
Don't believe everything that you think.
What are we offended about today?
Xsbank is offline   Reply With Quote
Old 02-02-2017, 04:19 PM   #20
Ted
Guru
 
Ted's Avatar
 
City: Campbell River
Country: Canada
Vessel Name: Okisollo
Join Date: Apr 2012
Posts: 643
You could use "regular" prop nuts and cast the anode over
them. Would need to melt it off to change prop.
See picture:

That prop has been on a long time, still good.

A PO (2nd back) said they didn't change the prop when they
changed the engine in 1988. Seemed to indicate that it's the same
prop when he saw it last summer. Don't know if it has been off
in the mean time or not. Don't think anyone will pull it if not
absolutely necessary as it's 53 inch diameter. I think it would
weigh about one and a half or two hernias.

Ted
Attached Thumbnails
Click image for larger version

Name:	IMG_0328.JPG
Views:	73
Size:	75.0 KB
ID:	61218  
__________________

Ted is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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





All times are GMT -5. The time now is 03:50 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012
×