FEBRUARY 2019

With much of the interior stripped out and the engine removed, it is the ideal time to inspect and replace all the through-hull fittings, starting with those below the waterline. These are critical to the safe and seaworthy operation of the vessel and their seals can and do break down over time. In addition, standards for their mounting and operation have changed over the past few years. It has been reported by others that perhaps 40% of the seacocks on private pleasure craft in the US are either inaccessible or seized up and inoperative. A stunning thought considering that a failure here can sink a vessel in a very short time.            

So, out they come, one at a time. 

Since the through hull’s are fitted with large bronze shutoff valves, there is obviously quite a strain placed on the hull mount so part of this exercise was to enable us to inspect the skin and core around each fitting and reinforce it as needed. The preferred style of seacock is a flange mounted style that connects directly to the through hull and provides a large surface area against the hull. This greatly reduces the stresses placed on the hull seal when operating the valve or if accidentally hit by an object. Here’s an example of such a fitting: 

  As you can see, it is securely mounted on a bonded backing plate.

First things first; come prepared. Here’s the selection of new pipe wrenches and other tools that were used.

The starting point was the stern area where there are two cockpit drains. Normally virtually inaccessible, they can now be reached by crawling over the empty engine mount. Here’s the hull under the cockpit after both drain hoses and seacocks were removed. The two through-hulls can be clearly seen.           

As you can see, the prop shaft had already been removed and the engine mount cleaned; more on that later.

We were wondering if these through-hull fittings had ever been replaced or re-sealed since the square mounting washer against the hull looked like a recent addition. Once they were removed it was obvious that they were.

Original cockpit through-hull, port side.

You can see two old screw mounts either side of the fitting and a definite oval shape still visible. There was plenty of caulk sealant to remove before the fitting could be twisted out of its hole. It looks like no water had seeped in from these two fittings but since there was past damage to the fiberglass skin we will be building up a new pad and resin sealing the hole through the core before we replace the fittings. It is now recommended that all through hulls have a backing plate on the inside of the hull to strengthen the overall bond and provide lateral support for any attached seacock.      

On the outside, the fitting was well secured with caulk but the hull surface skin around the opening will require some attention before a new fitting is added. To break the seal and remove the through-hull, I used a piece of steel angle as a key to engage with the tabs inside the fitting then twisted it with an adjustable wrench. Each brand of through-hull makes their own matching tool for this but without knowing the original product it was best to improvise. Besides, if they get damaged in the process it won’t matter since we are fitting new ones later.  And so we move on to the others….   

All had been fitted with the small, square backing plate that you can see in the picture and in most cases were not very well bonded to the hull. It’s important to remember that a seacock is not a gate valve or stopcock. It cannot be sourced from a plumbing store; it must be made of bronze not brass. Saltwater will corrode a brass fitting in no time and may well lead to a potential sinking. 

We will add new. larger backing plates, cut specifically for the purpose and bonded to the hull interior with epoxy. Once done, a semi-permanent sealant will be used to seal the fittings. We consider the use of a more aggressive, hardening sealer to be bad practice since its later removal, if required, will result in damage to the hull.         

March 2019 – Rudder hinge bolts; replacement.

Whilst we had access to the stern, it was decided to remove and replace the four quarter inch bolts that hold the rudder upper hinge and at the same time, add a stainless plate to spread the load across the keel. These four bolts have to take quite a load and access to them is almost impossible with the engine in place.

A piece of quarter inch 316L stainless steel plate was cut and drilled to match the four bolts protruding into the hull and after bedding down with epoxy, it was sealed in place using new 316L bolts and 4200 sealant. The original nuts were replaced with nylocs this time.

Later, whilst the boat is parked up, we will change all the external rudder hinge bolts since they are of a mixed selection of lengths and may have some degree of corrosion.

March 2019 – Through Hull repairs.

In the stern area, we are working on a method to repair the poor condition of the seacock mounts and have decided to tackle it as a two part process. First, build up the area around the opening to form a flat surface for the backing plate and second, to epoxy seal the hull opening. As part of this, we have used fairing compound to fill in the worst of the interior voids and to flatten out the hull curve. after that, it will be sanded and prepped for a layer of 1708 mat to make a solid, flat surface against which the backing plate can be bonded.

Once this is done, we will move to the outside and clean out the core around the hull opening and inject epoxy to solidify it.

The outer skin around the hull openings will need to be cleaned and repaired before new fittings added.

April 2019 – Continuing the through-hull repairs.

This week I’m making a concerted effort to get all the through hull openings cleaned of old sealant, sanded and then reinforced with new mat. Most of the hull skin around the each of the holes had been damaged by previous repairs and over-zealous tightening of the fitting, (probably to stop a slow leak). The plan is to clean each opening on both sides of the hull, repair any skin damage and use fairing compound to form a flat surface, suitable for the backing plates that will come next. The curved profile of the hull makes a flat-face sea-cock seal difficult to say the least and adding copious amounts of sealant and tightening the through hull until it crushes the hull skin is not the answer.

So as each opening is cleaned and sanded, it is getting some amount of fairing compound followed by 3-4 layers of 1708 mat to give the inside face the strength needed to hold a 1.5″ bronze sea cock. From the pictures you can see the skin damage found on the cockpit drain opening as well as old fixing bolt holes beside the openings that have been sealed up with who knows what. Once the inner surfaces have been strengthened and repaired, I will be adding backing plates to each hole to secure the new valves. We plan on using full-flange three bolt sea-cock valves and not the shut off valves that it came with. After all, we intend this replacement to be good for another 40 years and one less thing to worry about.

Here’s a look at the repairs done to the cockpit drain through-hull openings.

May 2019 – New fittings arrive.

Now that we have made progress with repairs to all the hull openings, its a good time to work how best to replace all the through hull fittings. Based on best practices, we’ve selected Groco flange valves for our seacocks, which will mate with their standard backing plates. So, to see how these will work in our spaces, I went ahead and ordered two of the 1½ inch and one of the 3/4 inch fittings, along with through hull’s. And here they are:

Now we will be able to assess the best orientation of the handles, what style of hose tail piece is needed and more importantly; how best to bond the backing plates in place. I expect that some of the through hull fittings will need to be trimmed down a little due to the thickness of our hull. We’ll see. All the original through hulls suffered damaged threads when they were removed so are unable to be re-used.