- Jul 10, 2020
- 161
- Boat Info
- 1981 310 Vanguard Express
- Engines
- Twin Mercruiser 6.2 MPI Horizon FWC inboards
My '81 Merritt Island boat, a 310 Vanguard, was fitted with Wilcox-Crittenden tapered cone seacocks for the engine raw water intake. It's very likely that factory used those seacocks for a number of years. They can stick solid, look incredibly crusty, and make you think about replacing them. But don't - they're extremely high quality and have an indefinite lifespan if properly cared for. Even if improperly cared for: you can bring them back from the dead very easily. Mine were stuck solid and I thought I was going to have to replace both, a serious effort when dealing with 43 year old through-hulls.
Bit of background first
Most modern seacocks these days have a ball valve inside. These work very well, can last a long time, and are widely available for replacement. They're not readily serviceable, have plastic internal fittings that can degrade, and once they fail they need to be replaced. Some shitty boatbuilders use gate valve seacocks: these look like the water shutoff valve in your house - they're actuated with a wheel. These are bad for many reasons, the biggest of which are that their design encourages crud to build up and make it impossible to close them after time, and you can't tell whether they're open or closed by looking at them.
But the gold standard is a bronze tapered cone seacock. This is a clever design that allows the unit to be lapped and refitted pretty much forever. It's extremely simple and reliable, bombproof, and can be bought back into service even after decades of neglect. The design is simply a cone machined of a very high quality 85-5-5-5 bronze with a hole bored through it. The cone fits into a corresponding conical hole in the body of the seacock. The cone rotates, bringing the holes into alignment with the intake and outflow holes in the body. The water seal is provided by a very very close fit between the cone and the body, which is achieved by lapping (grinding) the cone in situ periodically. Then grease keeps it moving, and also helps to further seal in the water. It's adjusted with a flange (thrust) nut that pushes on a keyed dog washer, these pull the cone tight into the body. A jam nut stops the flange nut from loosening. You can turn it with a captive handle or a pair of pliers or anything you want really.
Here's a diagram of the entire thing:
How they go wrong
Neglect. If you forget to grease them say once a year, they get increasingly stuff and hard to turn. Eventually they become so tight that they're hard to shift even with a breaker bar. If they were ball valves, that's where you'd be - upside down in the bilge with some PB Blaster, maybe a blowtorch (not at the same time!), a dead blow hammer, a breaker bar, and some prayers.
Grounding is also important. These are very high quality bronze components but you've got to ground them properly to avoid galvanic corrosion. Any sign of pink or red on the bronze is indication of the zinc in the alloy leaching out, which is almost only caused by galvanic corrosion. That can mean replacement if it's bad enough; certainly a sign to check grounds. Always ground to the flange screws that mount the seacock to the hull plate, never to the drain screw. It's common on older boats for the ground wires to get loose or fall out of their ring crimps. So check that.
Otherwise they don't go wrong.
It's stuck, now what?
Don't do this while in the water, or your boat will sink (and you with it since you'll be lying in the engine room under the deck.)
Assemble required things: lapping compound (Spartan Marine makes good stuff), a 15/16" and 7/8" wrench, seacock grease (Spartan Marine again), a mallet, seacock handle, mineral spirits, denatured alcohol, some clean rags.
Unscrew the jam nut - it's 15/16" hex. Then remove the flange nut, 7/8". Slide off the dog washer. The cone is now only held in place by force of habit. Put the jam nut back on to protect the threads of the cone bolt. Then with a combination of tapping the jam nut and gently tapping the seacock handle, you'll eventually get it to pop free. There'll probably be a stringer in the way preventing you from getting a hammer onto the jam nut, so you can fashion a lever from something suitably stiff and tap that instead. On my boat, I was able to free it just by tapping the seacock handle a couple of times. Then you can slide the cone out and it'll look like this, or worse:
Clean everything to get rid of residual grease. Mineral spirits works.
You're then going to apply a thin coating of lapping compound (basically liquid sandpaper) to the cone and reassemble, tightening the flange nut reasonably well but not so you can't rotate the cone at all. Make sure the flat on the dog washer is engaged properly with the key cut on the cone bolt. It may take some tapping and tightening to get the cone far enough into the body to expose the dog key.
Then rotate the seacock 10-20 times in one direction The first time is going to be quite difficult, then it'll slowly start to ease up as the lapping compound goes to work.
Once that's done, pull it apart again and clean up the lapping compound. I found denatured alcohol worked very well for this. The compound gets everywhere so be sure to work it out of the water holes in the body and inside the cone. Use fingers to dig it out. You really don't want it in there or it'll damage the valve every time you use it.
The cone will look nice now, an even bronze color with a smooth surface and very little staining. You're not creating a mirror so don't over-lap it. 10-20 turns is likely enough.
Then grease the cone and the inside of the body. nicely but not excessively and reassemble again. Tighten the flange nut to the point where you can operate the seacock with the handle but not so that it moves easily. You want to be applying an appreciable amount of force to the handle to turn it, but not so much that it's difficult. It should be something you can comfortably do one handed leaning down into the bilge but it should be deliberate.
Ongoing maintenance
The little drain screw, which can be used to drain the seacock over winter, is also an ideal place to use a grease gun during the season. You can unscrew it and put a zerk fitting/grease nipple on to make the process easy. Then when you're done, replace the screw.
If you see weeping or leaking, add grease. If that doesn't work then tighten the flange nut just until it stops (and of course the jam nut.)
You don't need to lap it every single winter, but it's not a bad idea to disassemble and re-grease at the end of the season. Lap only when tightening and grease don't stop weeping.
Stuck but boat is in the water
Remove the drain screw and squirt PB Blaster in there. Let that soak for a bit and then try to work the valve. This will work if the valve is open. If the valve is stuck shut, that's not going to do as much good because the PB will just fill the hollow cone rather than working its way between the cone and the body. But, it's worth a try. You can use the little red pipe on the PB to aim some of it to work between the two surfaces. Trying to use PB where the cone goes into the body is just wasting PB.
Further reading
I got a lot of this info from here before doing this myself: https://marinehowto.com/servicing-tapered-cone-seacocks/ Some of that info is specific to a different brand of seacocks than the ones in our boats. I'm also posting this here because that MarineHowTo site is the only place I found on the internet with any kind of explanation of tapered cone seacocks and how to service them, so if it shuts down then at least now there's another source for the next person with this problem.
Bit of background first
Most modern seacocks these days have a ball valve inside. These work very well, can last a long time, and are widely available for replacement. They're not readily serviceable, have plastic internal fittings that can degrade, and once they fail they need to be replaced. Some shitty boatbuilders use gate valve seacocks: these look like the water shutoff valve in your house - they're actuated with a wheel. These are bad for many reasons, the biggest of which are that their design encourages crud to build up and make it impossible to close them after time, and you can't tell whether they're open or closed by looking at them.
But the gold standard is a bronze tapered cone seacock. This is a clever design that allows the unit to be lapped and refitted pretty much forever. It's extremely simple and reliable, bombproof, and can be bought back into service even after decades of neglect. The design is simply a cone machined of a very high quality 85-5-5-5 bronze with a hole bored through it. The cone fits into a corresponding conical hole in the body of the seacock. The cone rotates, bringing the holes into alignment with the intake and outflow holes in the body. The water seal is provided by a very very close fit between the cone and the body, which is achieved by lapping (grinding) the cone in situ periodically. Then grease keeps it moving, and also helps to further seal in the water. It's adjusted with a flange (thrust) nut that pushes on a keyed dog washer, these pull the cone tight into the body. A jam nut stops the flange nut from loosening. You can turn it with a captive handle or a pair of pliers or anything you want really.
Here's a diagram of the entire thing:
How they go wrong
Neglect. If you forget to grease them say once a year, they get increasingly stuff and hard to turn. Eventually they become so tight that they're hard to shift even with a breaker bar. If they were ball valves, that's where you'd be - upside down in the bilge with some PB Blaster, maybe a blowtorch (not at the same time!), a dead blow hammer, a breaker bar, and some prayers.
Grounding is also important. These are very high quality bronze components but you've got to ground them properly to avoid galvanic corrosion. Any sign of pink or red on the bronze is indication of the zinc in the alloy leaching out, which is almost only caused by galvanic corrosion. That can mean replacement if it's bad enough; certainly a sign to check grounds. Always ground to the flange screws that mount the seacock to the hull plate, never to the drain screw. It's common on older boats for the ground wires to get loose or fall out of their ring crimps. So check that.
Otherwise they don't go wrong.
It's stuck, now what?
Don't do this while in the water, or your boat will sink (and you with it since you'll be lying in the engine room under the deck.)
Assemble required things: lapping compound (Spartan Marine makes good stuff), a 15/16" and 7/8" wrench, seacock grease (Spartan Marine again), a mallet, seacock handle, mineral spirits, denatured alcohol, some clean rags.
Unscrew the jam nut - it's 15/16" hex. Then remove the flange nut, 7/8". Slide off the dog washer. The cone is now only held in place by force of habit. Put the jam nut back on to protect the threads of the cone bolt. Then with a combination of tapping the jam nut and gently tapping the seacock handle, you'll eventually get it to pop free. There'll probably be a stringer in the way preventing you from getting a hammer onto the jam nut, so you can fashion a lever from something suitably stiff and tap that instead. On my boat, I was able to free it just by tapping the seacock handle a couple of times. Then you can slide the cone out and it'll look like this, or worse:
Clean everything to get rid of residual grease. Mineral spirits works.
You're then going to apply a thin coating of lapping compound (basically liquid sandpaper) to the cone and reassemble, tightening the flange nut reasonably well but not so you can't rotate the cone at all. Make sure the flat on the dog washer is engaged properly with the key cut on the cone bolt. It may take some tapping and tightening to get the cone far enough into the body to expose the dog key.
Then rotate the seacock 10-20 times in one direction The first time is going to be quite difficult, then it'll slowly start to ease up as the lapping compound goes to work.
Once that's done, pull it apart again and clean up the lapping compound. I found denatured alcohol worked very well for this. The compound gets everywhere so be sure to work it out of the water holes in the body and inside the cone. Use fingers to dig it out. You really don't want it in there or it'll damage the valve every time you use it.
The cone will look nice now, an even bronze color with a smooth surface and very little staining. You're not creating a mirror so don't over-lap it. 10-20 turns is likely enough.
Then grease the cone and the inside of the body. nicely but not excessively and reassemble again. Tighten the flange nut to the point where you can operate the seacock with the handle but not so that it moves easily. You want to be applying an appreciable amount of force to the handle to turn it, but not so much that it's difficult. It should be something you can comfortably do one handed leaning down into the bilge but it should be deliberate.
Ongoing maintenance
The little drain screw, which can be used to drain the seacock over winter, is also an ideal place to use a grease gun during the season. You can unscrew it and put a zerk fitting/grease nipple on to make the process easy. Then when you're done, replace the screw.
If you see weeping or leaking, add grease. If that doesn't work then tighten the flange nut just until it stops (and of course the jam nut.)
You don't need to lap it every single winter, but it's not a bad idea to disassemble and re-grease at the end of the season. Lap only when tightening and grease don't stop weeping.
Stuck but boat is in the water
Remove the drain screw and squirt PB Blaster in there. Let that soak for a bit and then try to work the valve. This will work if the valve is open. If the valve is stuck shut, that's not going to do as much good because the PB will just fill the hollow cone rather than working its way between the cone and the body. But, it's worth a try. You can use the little red pipe on the PB to aim some of it to work between the two surfaces. Trying to use PB where the cone goes into the body is just wasting PB.
Further reading
I got a lot of this info from here before doing this myself: https://marinehowto.com/servicing-tapered-cone-seacocks/ Some of that info is specific to a different brand of seacocks than the ones in our boats. I'm also posting this here because that MarineHowTo site is the only place I found on the internet with any kind of explanation of tapered cone seacocks and how to service them, so if it shuts down then at least now there's another source for the next person with this problem.