Replacing existing seacocks and filling deprecated holes

The bottom of the hull had many extra seacocks in it when we bought the boat.  Like most older boats, the chain of prior owners were none too careful about drilling holes in the bottom and sides, but once drilled they would never take the time to fill a hole that was no longer needed.  Since a huge number of "dock sinkings" are attributed to failed through hull fittings below the water line it was imperative to our refit efforts to replace all though hull fittings either above or below the water line and then fill the holes of extra through hull seacocks that were no longer going to be used OR which we wanted to move for one reason or the next.

IIRC we removed about 8 through hull fittings, with five of them being stuck in the closed position and one stuck in the open position.  Below is a picture of our second round of seacock removals so you can see what a nasty mess they were.  It doesn't matter what these went to but you can see that they are badly corroded.  #1 and #5 used backing blocks made of wood which was disintegrating.  #4 basically had no base and no block.  It was in no way approved for use as a seacock.  It would be fair to say it was a sunk boat waiting to happen.  None of these would have passed current ABYC requirements for withstanding 500 lbs of lateral force for 30 seconds.  When I went to test the engine seacocks with the previous owner watching he cautioned me not to pull too hard on the handles (even though they were very difficult to open) because he worried that the handle might break off.  And people wonder how boats sink at the dock...

Replacement of main engine seacocks.  
Just forward of the port engine the original setup had the seacock for the port engine as well as a separate seacock for the generator (which mounted amidships).  Given that we planned to move the generator to the starboard side and so that its weight would offset the fresh water tank opposite it on the port side it made sense to us to move the generator seacock.  The main engine seacock and strainer is circled below and the generator seacock and strainer is pointed to by the arrow.  Both of these seacocks were clapped out and the seawater strainers were beyond their service life as well.

We decided to replace the main engine seacocks with Groco SBV1500 units that contain the removable service plug for out of water testing, winterizing until we can leave Virginia, and maintenance.  With this side port option we can leave fresh water in the engine's raw water system between trips to the boat even though it will be docked in salt water in the Bahamas.

These Groco seacocks don't come cheap but they will pass all safety standards and we like the heavy bronze handles that will accept a 3/8" socket wrench head if you need more leverage moving them.  We plan to regularly maintain the ball unit in these to preserve our investment.  We paired these 1-1/2" seacocks with Groco backing plates which have built in bronze nuts.  The notion is that you can 5200 the backing plate in place, screw a scoop fitting in tight from the bottom, and then bolt the seacock to the backing plate for a very strong installation.  We also glassed the backing plates to the boat as you will see later for an overkill job on these seacocks.  In the future if they ever get stiff on us I don't want to have to worry about using a breaker bar to get them moving again.  We replaced the old bronze strainers with modern Forespar Marelon ones.

We then moved the engine seacock to where the generator seacock had been because it allowed for a shorter hose to the engine raw water pump with fewer bends in it.  The area around both of the holes was sanded in order to get access to clean fiberglass.

The seacock base was then bedded with 3M 5200 and then glassed in with West System epoxy resin and layers of #17 cloth before installing the scoop underneath the boat. I think you will agree, that engine seacock is never going anywhere...

Underneath the boat we needed to fill the generator hole, so the area around the hole was prepared by using a grinder with 36 grit flap wheel to taper the sides of the hole into the center.  We read online that the area to taper (AKA "to scarf") should be a diameter 12x as large as the hole in order to assure maximum strength.  It sounded like overkill but we like overkill when it comes to the bottom of the boat.  Unfortunately, the full 12:1 of the 1-1/2" hole would have been 18" and that would have gotten us into the area of the engine seacock hole.  Instead we went with about 11" diameter taper for this hole.  That along with reinforcement from above will bring us back up to the desired overkill.

We built the patch up in layers using concentric circles of #17 cloth.  Each layer was laid in with West Systems epoxy and then the air was squeegeed from each layer using wax paper and a Bondo spreader.

After gooping the tapered portion with epoxy resin, we then applied the patch using the waxed paper to position it into place and then to squeegee it free of bubbles for the last time.

When cured it was sanded fair, filled to remove miner holes and then gel coated again as a moisture barrier.  Up in the engine bay, glass was added on top of the patch to make a nice sandwich out of it. Eventually it will receive a new barrier coat and then bottom paint.  We ended up filling multiple holes on the bottom using this method.

Click here to see how we used a similar process to patch an old blower vent hole in the side of the boat.