Author Topic: Backing plates and thru-hulls  (Read 4561 times)

Bill Bischoff

  • Full Member
  • ***
  • Posts: 167
    • View Profile
  • Boat Type: CSY 44 WO
  • Boat Name: Odyssey
Backing plates and thru-hulls
« on: June 28, 2012, 07:23:48 pm »
Hi all,

Odyssey is currently hauled for bottom work, so I thought this would be a good time to replace the saturated wooden backing plates on the thru-hulls/seacocks.
Odyssey, 1979 44 WO
Lying La Paz, BCS

Peter Roach

  • Moderator
  • Hero Member
  • *****
  • Posts: 810
    • View Profile
  • Boat Type: CSY 44 WO
  • Boat Name: Grace
Backing plates and thru-hulls
« Reply #1 on: June 28, 2012, 08:14:38 pm »
Just to give another view of the same project:

Two weeks ago I replaced my backing plates with fiberglass backing plates. I also replaced the thruhulls and rebuilt all of the valves. It was quite a job! A couple of tips:

I pounded out the keeper bolts on the valves and then disassembled the valve in the boat. I used a soft lumber 2X4" (cut down to fit) to place inside the valve body and use as a lever to spin them off of the thruhull.

I used one of those vibrating cutters (Harbor Freight) to remove the old backing plates and most of the 5200. I used a 5 in 1 tool (high tech putty knife) to remove a lot more of the 5200 and finally a bronze wire brush on my drill to get the rest off. I used 3M adhesive remover to help get everything clean.

With the old thruhulls in place I put my fiberglass backing plate in and spun the valve back onto the thruhull. I used a thick piece of paper to determine where any gaps were so I could grind down the back of the fiberglass backing plate to ensure that the inside and outside of the hull was square. There were lots of times up and down the ladder. When I got it reasonably square on the backing plates. I then 5200 the fiberglass backing plates to the hull and spun the valves down onto the thruhull.

Removing the thruhulls (now you are probably asking why do I need to remove the thruhulls? Good question. Unless the backing plate is exactly the same thickiness as the one you are taking out your handles are going to be in the wrong place. You have to mount the valve where you want it and then spin the thruhull into the valve from the outside - you definitely need a machine shop to cut down the new thruhulls to fit. My machine shop charged me $25 to cut down all of the thruhulls) To remove the old thruhulls I use an open / closed end wrench. I inserted the open end into the thruhull down to where the tits are and then put a screw driver in the open end and spun them out of the hull. It was easier than I expected. I then cleaned up the hole of any 5200. It came out quite easy.

I then cleaned, lapped, greased, and reassembled the valves. I bought new bronze carriage bolts to replace the ones that were holding the old valves in place. These are not cheap! I drilled out the keeper holes from the outside to the inside of the boat. I then mounted the valves with the carriage bolts. I had the new thruhull in place loosely when I did this step.

I then placed 5200 around the bottom inch of the thruhull (part toward the mushroom end). Work the 5200 in well so there is no wicking through the threads. I put liquid Teflon (NAPA) on the top of the thruhull threads. This was in case it was tempted to leak. I was careful not to get the tefelon on the fiberglass as I inserted it and then spun the thruhull onto the valve using my open / closed end wrench.

Cleaned up everything with Disolveit and repainted the thruhulls (except for the two big ones that are used for the cockpit scuppers. I plan on using these for grounding my SSB and I wanted them raw bronze.

The entire job took me about a week. I had a helper for the mounting of the valves and installing the new thruhulls.

A couple of notes. I had a heavy duty bucket without a handle that I used for a stool inside the engine compartment. It was a life saver. I used a wire brush on a grinder to clean up the old thruhulls. Don't use this on the inside of the valve housing or the cone or you can really mess up them. The lapping compound was from NAPA. I got the fiberglass backing plate from an old sailboat hull that was being cut up. They are cutting up a lot of old boats in Green Cover Springs Marina. If you need fiberglass they can sell you some. Ask for it in long boards so you can run it through a plainer. I used a belt sander and it took FOREVER to sand it down flat. I used a grinder with a cutting wheel to shape the fiberglass. It actually went quite fast. Remember to only tighten the valves a little. The grease does the work not the mechanical tightening.

I had another post on this subject. You might want to look it up to see if I had any other suggestions
I tried having a bad day once but I did not like it

Thane

  • Sr. Member
  • ****
  • Posts: 95
    • View Profile
Backing plates and thru-hulls
« Reply #2 on: June 28, 2012, 08:36:12 pm »
Anybody considered using starboard as material for the backing plate?
Thane Gilliam
Heart of Gold
44 W/O

Peter Roach

  • Moderator
  • Hero Member
  • *****
  • Posts: 810
    • View Profile
  • Boat Type: CSY 44 WO
  • Boat Name: Grace
Backing plates and thru-hulls
« Reply #3 on: June 28, 2012, 10:52:28 pm »
As I understand it Starboard is too plyable. If put under pressure it will keep moving. Not sure if this is true. Let us know if you try it.
I tried having a bad day once but I did not like it

Donald Stengel

  • Guest
Backing plates and thru-hulls
« Reply #4 on: June 29, 2012, 07:48:23 am »
My reading on starboard for backing plates is nothing sticks to it. None of your sealants will adhere to the starboard. I think this in a Don Casey book I read.
Donald

Bill Bischoff

  • Full Member
  • ***
  • Posts: 167
    • View Profile
  • Boat Type: CSY 44 WO
  • Boat Name: Odyssey
Backing plates and thru-hulls
« Reply #5 on: June 29, 2012, 01:50:49 pm »
Peter, we did many things the same in this project.
Odyssey, 1979 44 WO
Lying La Paz, BCS

Jules Shockley

  • Moderator
  • Sr. Member
  • *****
  • Posts: 163
    • View Profile
  • Boat Type: CSY 44 W/O
  • Boat Name: Dragon Lady
Backing plates and thru-hulls
« Reply #6 on: June 29, 2012, 09:05:39 pm »
For future reference, there is a product called DeBond that will melt 5200, even in a hard to get to joint. Just spray it on and it slowly eats it way in. Then a 5 in 1 tool will finish the job...But it ain't cheap.
Jules

Bill Bischoff

  • Full Member
  • ***
  • Posts: 167
    • View Profile
  • Boat Type: CSY 44 WO
  • Boat Name: Odyssey
Backing plates and thru-hulls
« Reply #7 on: June 29, 2012, 09:53:38 pm »
Jules, I would have paid big $ to not have to remove the 5200 manually.
Odyssey, 1979 44 WO
Lying La Paz, BCS

Rhapsody

  • Hero Member
  • *****
  • Posts: 279
    • View Profile
Backing plates and thru-hulls
« Reply #8 on: June 30, 2012, 07:37:47 am »
I used starboard for a backing plate on the head intake. Used 101 sealant the first time and it "stuck" to the material pretty good for 4 years, no leaks. Had to replace the seacock a few days ago as there was a recall on it: http://www.groco.net/svc-bltn/cat-svc-bltn-2-08.htm

Used 4200 Fast Cure for the new seacock, the marine store said 101 is no longer in production....

Used marine plywood with 2 coats of West System epoxy for other throughhull backing plates.

Bill Bischoff

  • Full Member
  • ***
  • Posts: 167
    • View Profile
  • Boat Type: CSY 44 WO
  • Boat Name: Odyssey
Backing plates and thru-hulls
« Reply #9 on: July 24, 2012, 07:33:43 pm »
Hi all,

I received a call today from the boat yard advising me that they had tried to splash my boat, but had to haul it back out due to numerous leaks at the seacocks.
Odyssey, 1979 44 WO
Lying La Paz, BCS

Peter Roach

  • Moderator
  • Hero Member
  • *****
  • Posts: 810
    • View Profile
  • Boat Type: CSY 44 WO
  • Boat Name: Grace
Backing plates and thru-hulls
« Reply #10 on: July 24, 2012, 10:06:06 pm »
Remember the grease does the work of keeping the water out not the mechanical pressure. Don't over tighten the thru hull bolts.

Also, If you have the original bronze ones you might want to pick up a set of "service' wrenches to tighten the nut while holding the flange nut with the service wrench. A service wrench is a thin wrench that will fit the thin nut that is attached to the flange.
I tried having a bad day once but I did not like it

Bill Bischoff

  • Full Member
  • ***
  • Posts: 167
    • View Profile
  • Boat Type: CSY 44 WO
  • Boat Name: Odyssey
Backing plates and thru-hulls
« Reply #11 on: July 24, 2012, 11:44:15 pm »
Peter, thanks for the advice.
Odyssey, 1979 44 WO
Lying La Paz, BCS

Peter Roach

  • Moderator
  • Hero Member
  • *****
  • Posts: 810
    • View Profile
  • Boat Type: CSY 44 WO
  • Boat Name: Grace
Backing plates and thru-hulls
« Reply #12 on: August 17, 2012, 12:43:46 pm »
I posted the picture of the rebuilt thruhull with the fiberglass backing plate on Dropbox

CSY Info
I tried having a bad day once but I did not like it

Soggy Geek

  • Administrator
  • Hero Member
  • *****
  • Posts: 562
    • View Profile
    • Cruise Around the World with Soggy Paws
  • Boat Type: CSY 44 WT
  • Boat Name: Soggy Paws
Backing plates and thru-hulls
« Reply #13 on: September 30, 2012, 11:42:43 am »
There are a number of step-by-step illustrated "How To" articles relating to Seacocks on this most excellent website from Compass Marine:

http://www.pbase.com/mainecruising/boat_projects
Soggy Paws the CSY has been sold but not forgotten!
http://svsoggypaws.com/CSY/