You want to make sure that the intake will not be located directly in front of any of those items, as the disruption to the flow of water can alter their performance. Also, be sure you have enough clearance on both the inside and outside of the hull. It helps to pick a landmark, like an existing fitting or component, that is visible on the exterior of the boat as well as in the bilge compartment. Usually, the outside isn't an issue because you'll be doing the install with the boat on the trailer, and bunks are the biggest obstacle here.
Inside you need to have sufficient room not only for the components that will attach to the thru-hull but also for the installation. Remember, you'll need more room for all of your parts to be assembled than they will occupy once installed. Once you've determined the ideal location for the intake, apply masking tape to the exterior of the hull extending out from the intended location by at least six inches.
Applying masking tape will serve two purposes; first, it will prevent damage to the surrounding area if the bit happens to slip, and second, it will prevent splintering of the gel-coat which is the exterior colored surface of the boat's hull that gives it the smooth glassy appearance.
If your boat has a finished bilge liner Malibu direct drive models for example , you'll also want to mask off the interior where the penetration will be for the same reasons outlined above. Step 2: Drilling the Pilot Hole Well, the hard work is done, now it's time to drill the hole.
While incredibly simple and straight forward, this step is the most intimidating, so just make sure you've placed the fitting correctly above and take your time. The first step in the drilling process is to drill a pilot hole for the hole saw bit you'll be using. Starting from the exterior, use the same size drill bit as the pilot bit on the hole saw you'll be using to drill through the hull of the boat.
Step 3: Drilling the Final Hole Now that you've got a hole that extends all the way through into the bilge of the boat, you can score the fiberglass on the inside to prevent chipping when the hole saw bit finished the cut. An impact driver is a great tool that will tighten the nuts without having to have a second person outside the boat with a screw driver.
Once the nuts are tight climb back out of the boat and remove the thru-hull fitting. Clean it with Acetone then lather it up with a marine sealant of your choice. Now use a step wrench, and a large adjustable wrench, and tighten the thru-hull into the flange from outside the boat.
Once everything is tight clean up the ooze from the sealant, including any that oozed out up inside the through hull and around the exterior. I would avoid the use products or fillers like Bondo or Evercoat below the waterline as they can absorb moisture.
So why do I use Sikaflex sealants or bedding compounds rather than 3M products? There really is little to no need for a sealant as permanent as 3M I suspect 3M was invented to ensure future boatyard revenue. As you can see in this photo the silicon bronze bolt heads are countersunk and most of the excess Skiaflex sealant has been wiped away. Some boats do not have thick enough hulls for this! The next step is to fair over the bolt heads with 3M Marine Premium Filler to get a nice smooth hull with no visible bolts.
After the fairing step I also did a complete barrier coat of the area for added moisture protection using Interlux Interprotect series barrier coat.
This is a photo of a one year old yellow brass Home Depot ball valve installed by the previous owner. When I asked this seasoned boating veteran why he used a ball valve from Home Depot he said;. This Home Depot valve was in use for about 8 months, of total in-water time, and the ball, inside the valve, was completely gone, not there, corroded away.. This valve was literally weeks away from catastrophic failure of the boat sinking type. This is after only eight months of use.
Again please do not cheap out on your below water metals. It is not too difficult to get a decent color match, this one I did by eye, and it was just about spot on. Always stir waxed gelcoat before you dip your brush or roller in.
This will keep the wax thoroughly mixed. Personally, I am not a fan of paint in a bilge area, but if you are, you can use that too. I simply prefer the durability and bonding of gelcoat over paint in damp areas. This is the finished product after a few seasons use. I prefer to use heavy duty mandrel formed marine hose , such as Trident or Shields, for all below waterline connections.
Remember to close your seacocks when you leave the boat. Replacing Thru-Hulls and Seacocks. A Poor Idea The picture on the left is what not to do if starting from scratch and installing new seacocks. A Much Better Idea While both this photo, and the previous photo, were taken on my workbench the plywood is representative of the hull of your boat and the bronze fittings of two very typical installation methods used today.
Removing the Old Thru-Hulls This is the easy part of the project but you will need a few tools first. The must have tool for this project is called a step wrench. The step wrench can be inserted into the thru-hull and then used to tighten it into a seacock or to remove it from a seacock. With the use of some heat you can also use it to break the marine sealant free from the hull. Most step wrenches have a nice flat spot for a pipe wrench or adjustable wrench for added leverage. The photo shows the step wrench inserted into the female side of the thru-hull ready to tighten or loosen.
The Dogs This photo shows the dogs or ears inside the thru-hull that allow the slot on the step wrench to grab hold and break it free or tighten it. Fiberglass Backing Plates: To make solid fiberglass backing plates you will need the following items.
Fiberglass in both 18oz Woven Roving and a standard 6oz Fiberglass Cloth. A 24 X 24 inch piece of relatively thick glass. A Fiberglass roller.
Mold release wax for the glass. What about Starboard? Starboard is far to flexible to offer any sort of rigid stiffening to the hull. It does not stick well to any adhesives, which includes bedding compounds such as , or Sikaflex and the manufacturer even backs this up. Starboard backing blocks can lead to leaks below the waterline! The concept of a backing plate is to become one with the hull, make it thicker and add stiffness so the seal between the hull and through hull is not compromised and does not flex or move.
Starboard fails in all these areas.. Cut Your Backing Plates After the fiberglass board has cured you can then proceed to drill your backing plates.
More Tools In any job the correct tools will save you money in the long run. What is a Seacock?? The flanged adapter is a relatively new concept in seacock technology from Groco. Dry Fit For this particular valve I unfortunately had very little clearance and needed to turn 90 degrees. Dry Fitting The Seacock Now that your backing plate is installed and cured the first thing to do is to drill your hole for the thru-hull.
Measuring for thru-hull length: 1- With the thru-hull bottomed out into the flange measure from the outside of the hull to the mating side of the mushroom-head. Countersink The Flange Side In this photo I still need to countersink the flange side of the bolt holes slightly.
Exterior View of Installed Thru-Hull As you can see in this photo the silicon bronze bolt heads are countersunk and most of the excess Skiaflex sealant has been wiped away. The transducer you select must be compatible with your fishfinder and include the specific capabilities you desire. It must also be compatible with your boat's hull material. Bronze transducers are recommended for fiberglass or wood hulls. Plastic transducers are recommended for fiberglass or metal hulls.
Stainless steel transducers are recommended for steel or aluminum hulls. When installing a stainless steel transducer into an aluminum or steel hull, care must be taken to isolate the transducer from the hull to prevent galvanic corrosion. Plastic transducers are not recommended for wood hulls, since the expansion of wood can damage a plastic transducer.
Your fishfinder owner's manual will help you in this regard. B bronze thru-hull with standard fairing block. Mounting your transducer in an incorrect location can cause a problem due to turbulence, air bubbles and obstructions such as the boat's keel.
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