Replaing Seacock Backing Plates

[jbenagh]

Oh, one other important detail: all the 3/4 in thru hulls go through a lot of layers of stuff. I needed to buy the extra long ones at $33/ea instead of $12/ea. Anyone want to buy three 3 in long 3/4 thru hulls?

Jeff

[gates_cliff]

Restarting this thread.

I had been monitoring water in the bilge of my boat very closely since we've had so much rain the past few weeks, well the entire summer. I felt pretty smug because the bilge had been pretty dry, I keep a turkey baster on the boat just get all the water out of the bilge. Was down yesterday and had more water than normal, tested the bilge pump and switch to make sure they were working ok and they were. So, started looking around and noticed there was a slight leak from the galley sink drain seacock. It appears to be coming from one of the bolts that attaches the seacock to the the thru hull. There is an existing plywood backing plate and it doesn't look to be in great shape.

I had hoped to keep my boat in the water until at least mid November but am now leaning toward hauling out now so as not to risk a minor problem turning into an emergency.

So, I'm guessing I'm going to have to go through the same process that all of you have described. As to the backing plate, I Would lean toward getting some "502" from McMaster Carr, would it be possible to cut this out using a hole saw? I've never worked with it before.

[John Stone]

Hi Cliff
I don’t know what 502 is. Did you mean G10? If so you. Can get it from McMaster Carr. Generally you will want 1/2” thick. Yes, you can cut it with a hole saw.

John

[jbenagh]

Generally you will want 1/2” thick. Yes, you can cut it with a hole saw.

I found I could almost cut 3/4 G10 with a hole saw but a tabletop drill press didn't work. Neither did a hand drill, even a big one with two handles.
I ended up starting with a 6in (or 8in) hole saw to get a center hole and a score line but then used a bandsaw to complete the cut. I did use up a 1/4in bandsaw blade though.

The hole saw worked great for the center holes though.

Jeff

[John Stone]

Why are you using 3/4” G10? All you need is 1/2” max. Stuff is like steel. You’re just trying to spread the load over a wider area and have a flat surface for the bottom surface of the seacock.

[Jeff and Sarah]

I’m in the middle of this project on my 28’ CD Trawler. I used 1/2” GPO-3 from McMaster Carr. My plates are all 5 1/2” and cut easily on my drill press with light pressure and a slow bit speed. My backer plates are all installed but I won’t bother drilling them for the through-hulls until I complete the bottom job.

Side note: While removing the seacocks another boat owner approached me in the yard. He has some type of I/O cruiser I think. He asked me how I removed the through-hulls and I told him I unscrewed them from the seacocks with a step wrench. His response was “Ooh- that’s not good. You shouldn’t be able to do that. Normally you need to cut them out with a hole saw.” It made me laugh. Everyone is an expert these days and I’m sure he’s offered advice to other boaters who mistook his confidence for knowledge.

[jbenagh]

Why are you using 3/4” G10? All you need is 1/2” max.

Because I didn't read other people's recommendations closely enough

Also, the plywood I replaced was 3/4 so that was what I picked. If I did it again I would definitely do 1/2"

Jeff

[John Stone]

That's never happened to me.

Nice job. Better than the boatyard would do.