Marine Hardware Analyst Agrees With This Being the Best Way to Install Seacocks 

Raritan Engineering Company your marine hardware specialists would like to share with you these topics we thought would be of interest to you this month regarding the best way to install seacocks.

Marine Hardware Experts Have Best Way to Install Seacocks shK1zt

Your marine hardware expert’s best advice for anyone contemplating adding a through-hull fitting is don’t. Through-hulls sink boats. If you can accomplish the same thing by installing a tee-connector in an existing inlet or discharge line, you avoid boring another hole in the bottom of your boat.

New Through-Hull

As your boat hardware and accessories outlet we know that installing a new through-hull fitting necessitates a new hole in the hull. Always locate seacocks where they are readily accessible or you defeat the purpose of having a valve in the line. Before you drill the hole, double-check the location carefully both inside and outside the hull to make sure, for example, that inside there will be ample room to throw the handle, and outside the new fitting is not going to set up turbulence in front of your depth sounder or speed log impeller.

Select a hole saw the size of the fitting you are installing and cut the required hole by first drilling from the outside of the marine hull until the pilot drill in the hole saw penetrates the hull, then finish the hole by drilling from the inside.

Through-Hull Replacement

To replace a through-hull fitting, remove the nuts from the bolts through the seacock’s mounting flange and unscrew the bolts or drive them out with a hammer and a punch. Unscrew the seacock from the through-hull-with the help of a marine pipe wrench, if necessary.

You can find more information as well as get assistance on marine hardware supplies and a marine water heater and on how to find the best way to install a seacock at Raritan Engineering.

Marine Hardware Adviser Gives Thumbs Up on These Suggestions

Through-hull fittings installed with polyurethane sealant can be very difficult to remove. A length of 3/8-inch threaded rod (or a long bolt) which is a nice piece of hardware, will make the job easier. Slide a washer or a metal plate too big to pass through the fitting onto the rod and capture it with a nut. Pass the rod through the fitting from inside the boat, seating the washer flat on the fitting. 


Once the hole is prepared, the remaining steps are identical for a new seacock or a replacement. Cut a circle of 3/4-inch plywood 2 or 3 inches larger than the flange of the seacock, and bore out the center with your hole saw to form a ring.

Because you are going to thread the through-hull into the seacock, you can discard the lock nut. Insert the new through-hull fitting from outside the marine hull, then inside slip the wooden ring in place and thread the seacock onto the through-hull.

Tighten the two parts together. Most boatyards have a special step-wrench that grips the ears inside bronze through-hulls. A wedge of scrap hardwood will do the same job.

With the seacock tightened snugly–not too tight–you should have plenty of threads inside the seacock, but the length of the through-hull should not prevent the base of the seacock from tightening against the plywood ring hardware. If the through-hull is too short, replace the 3/4-inch thick ring with a new one cut and shaped from 1/2-inch plywood.


Insert the through-hull, put the hardware plywood ring(s) in position, and insert the mounting bolts through the hull and far enough into the plywood to prevent it from turning. If the seacock is bronze, the mounting bolts must also be bronze.

Tighten the seacock until it seats snugly on the ring and the mounting holes are in alignment. Remove the mounting bolts and heavily coat them for an inch or so below the heads with polyurethane sealant. Reinsert them through hull, ring, and flange, and install a washer and a nut on each.

So don’t forget these steps needed in installing a seacock. 1) New through-hull;  2) through-hull replacement;  3) dry fit;  and then 4) installation.

Raritan Engineering your marine parts depot has more information on marine hardware such as a boat water heater and the best way to install seacocks. See our extensive line of marine products on our website.

via Installing a Seacock

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