Im process of updating a 81 27' Catalina with the orginal thru hulls. What needs to be done with the volcano type thru hulls. Drill out with a hole saw? Grind the "volcano" flush? Does a reinforment pad then need to be built up? What is used to seal the new fitting, 5200? This boat is a northern fresh water boat now going into salt water, if the bronze thru hull strainer appear to have minimum corrosion is replacement necessary?
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Garry @ S/V TASHTEGO
Thru Hulls
I have written on this before and you can look in the archives. But here's what you need to do. You need to have the boat hauled. You need the following tools: a medium sized pipe wrench and a hammer for loosening the old gate valves. A big pipe wrench won't be useful in the close quarters you'll be working in. Since you won't have the leverage of a big wrench you may need in persuasion of the hammer. An electric hand held grinder to grind down the old volcano (and saw off the old pipe inside). A carbide hole saw for each of the thru hull sizes you will replace (cutting fiberglass will dull a steel hole saw like lightening). Plenty of 4200 (not 5200 which will not allow disassemble when needed). Remove the hose from the valve. Use the pipe wrench (and probably the hammer) to remove the valve. It helps to disassemble the valve down to just the body by unscrewing the mechanism that the stem passes through. You might get lucky, when I started to turn the 3/4" head intake valve the pipe started to unthread from the volcano so I just yanked it out. The sink/ice box pipe refused to budge. If there is already a thruhull in place you have to decide whether or not to use it. TASHTEGO had a 1 1/4" head pump out but while removing the valve it turned in the hull and broke the seal. I decided to remove the thru hull and replace it. This was a difficult chore as getting the pipe wrench on the nut was hard and it turned. Since I was doing the job alone I made a wrench to fit down through the thru hull and engage the knobs on the inside near the other end. It was an old 3/8" drive socket that just fit into the ID of the thru hull. I ground notches into the socket with the grinder to fit over the knobs. If you look into your thru hull you'll see these knobs on the ID. With all of the hardware out I proceeded to grind down the volcanos with the Makita grinder. Don't go crazy and grind holes in the hull, just get it fairly flat. Next, use the carbide edge hole saw to cut the appropriate size hole drilling from the outside in. I used a 1 1/8" Remgrit hole saw for the 3/4" thru hull for the head inlet and the old hole for the pump out. You will have a very difficult time starting the hole saw without something in the hole for the pilot bit to engage. I used one of the tapered plugs sold for plugging broken thru hulls, etc. Put it in from the inside using one just big enough to project 1/2" or so on the outside then start the hole saw's pilot drill in the center of the plug and away you go. If you had to grind off the old volcano with the pipe inside the hole saw will remove the remaining ring of bronze when the new, larger, hole is cut. Once the new hole is cut, clean the outside surface around the hole very well, sanding down to a good surface and removing all of the anti fouling paint for at least 1/2" around the outside of the thru hull. Then mix up some penetrating epoxy and coat the raw edges of the hull in the hole. When the epoxy is set (this took some time for me i.e., overnight, as the weather was cool) slather the mushroom head with 4200 and stick it in the hole. Run inside, slather 4200 around the thru hull on the inside, start the nut on the thru hull and snug it up by hand. If you have made a wrench for the thru hull you can go on and tighten it up until it is good and tignt with the pipe wrench on the outside and the internal wrench going down the inside. Otherwise you'll have to find some other way to hold the thru hull still while you tighten it up. Some folks advise waiting a day then giving the nut a tweak to compress the 4200. I figure this will break any adhesive seal so I go directly to full tight. Now you have to mount the sea cock. You can just use a ball valve on the thru hull but you shouldn't. The thru hull has a straight thread and the valve will have a tapered thread, not a good combination. Bite the bullet and get a flanged seacock which is straight thread on the bottom and tapered thread on top. The thru hull is almost certainly too long for the sea cock to bottom out on the hull when screwed down all the way. You will have to make mounting pads for them. I made mine out of teak saturated with epoxy. They should be thick enough to support the base of the seacock when screwed down tight but not so thick that they only let a few threads engage. This was a trial and error process with router and hole saw. When making the bases I drilled a small pilot hole through the center of the block then cut them circular on the outside with a circle cutting attachment to my router. Using the same circle cutting attachment and the pilot hole, I cut a recess in the base for the thru hull nut. If you don't do this the wooden base will sit on top of the nut and not be an effective support. Now turn the base over and drill a hole for the threaded part of the thru hull using the same hole saw you used to cut the hole in the hull. The result should be a donut of teak that fits over the thru hull and goes all the way down to touch the hull. Now take off the donut and screw on the sea cock and count the turns until it seats. Unscrew and try it with the donut in place. Cut down the donut until the thru hull engages almost all of its threads. When you have the donut cut to size give it a coat of penetrating epoxy then a coat of regular epoxy following the instructions. You can buy small epoxy kits at West Marine that should be just enough to do all of the thru hulls on a Cat 27. For final assembly glue the donut to the hull with 4200 and attache the sea cock with plenty of teflon tape. For security I drilled a pilot hole and used a 3/4" stainless lag screw to attach the thru hull flange to the donut. Don't drill right through the hull when drilling the pilot hole. You will have to buy and install a tail piece with pipe threads on one end and a hose barb on the other. Use plenty of teflon tape here too. Attach the hose using double hose clamps and consider replacing the old hose at this time. Once I figured out what was what I did the engine intake (replacing the scoop strainer thru hull) and the sink/ice box thru hull in about an hour for each. I have photos and I will put them in the photo gallery soon.
I have written on this before and you can look in the archives. But here's what you need to do. You need to have the boat hauled. You need the following tools: a medium sized pipe wrench and a hammer for loosening the old gate valves. A big pipe wrench won't be useful in the close quarters you'll be working in. Since you won't have the leverage of a big wrench you may need in persuasion of the hammer. An electric hand held grinder to grind down the old volcano (and saw off the old pipe inside). A carbide hole saw for each of the thru hull sizes you will replace (cutting fiberglass will dull a steel hole saw like lightening). Plenty of 4200 (not 5200 which will not allow disassemble when needed). Remove the hose from the valve. Use the pipe wrench (and probably the hammer) to remove the valve. It helps to disassemble the valve down to just the body by unscrewing the mechanism that the stem passes through. You might get lucky, when I started to turn the 3/4" head intake valve the pipe started to unthread from the volcano so I just yanked it out. The sink/ice box pipe refused to budge. If there is already a thruhull in place you have to decide whether or not to use it. TASHTEGO had a 1 1/4" head pump out but while removing the valve it turned in the hull and broke the seal. I decided to remove the thru hull and replace it. This was a difficult chore as getting the pipe wrench on the nut was hard and it turned. Since I was doing the job alone I made a wrench to fit down through the thru hull and engage the knobs on the inside near the other end. It was an old 3/8" drive socket that just fit into the ID of the thru hull. I ground notches into the socket with the grinder to fit over the knobs. If you look into your thru hull you'll see these knobs on the ID. With all of the hardware out I proceeded to grind down the volcanos with the Makita grinder. Don't go crazy and grind holes in the hull, just get it fairly flat. Next, use the carbide edge hole saw to cut the appropriate size hole drilling from the outside in. I used a 1 1/8" Remgrit hole saw for the 3/4" thru hull for the head inlet and the old hole for the pump out. You will have a very difficult time starting the hole saw without something in the hole for the pilot bit to engage. I used one of the tapered plugs sold for plugging broken thru hulls, etc. Put it in from the inside using one just big enough to project 1/2" or so on the outside then start the hole saw's pilot drill in the center of the plug and away you go. If you had to grind off the old volcano with the pipe inside the hole saw will remove the remaining ring of bronze when the new, larger, hole is cut. Once the new hole is cut, clean the outside surface around the hole very well, sanding down to a good surface and removing all of the anti fouling paint for at least 1/2" around the outside of the thru hull. Then mix up some penetrating epoxy and coat the raw edges of the hull in the hole. When the epoxy is set (this took some time for me i.e., overnight, as the weather was cool) slather the mushroom head with 4200 and stick it in the hole. Run inside, slather 4200 around the thru hull on the inside, start the nut on the thru hull and snug it up by hand. If you have made a wrench for the thru hull you can go on and tighten it up until it is good and tignt with the pipe wrench on the outside and the internal wrench going down the inside. Otherwise you'll have to find some other way to hold the thru hull still while you tighten it up. Some folks advise waiting a day then giving the nut a tweak to compress the 4200. I figure this will break any adhesive seal so I go directly to full tight. Now you have to mount the sea cock. You can just use a ball valve on the thru hull but you shouldn't. The thru hull has a straight thread and the valve will have a tapered thread, not a good combination. Bite the bullet and get a flanged seacock which is straight thread on the bottom and tapered thread on top. The thru hull is almost certainly too long for the sea cock to bottom out on the hull when screwed down all the way. You will have to make mounting pads for them. I made mine out of teak saturated with epoxy. They should be thick enough to support the base of the seacock when screwed down tight but not so thick that they only let a few threads engage. This was a trial and error process with router and hole saw. When making the bases I drilled a small pilot hole through the center of the block then cut them circular on the outside with a circle cutting attachment to my router. Using the same circle cutting attachment and the pilot hole, I cut a recess in the base for the thru hull nut. If you don't do this the wooden base will sit on top of the nut and not be an effective support. Now turn the base over and drill a hole for the threaded part of the thru hull using the same hole saw you used to cut the hole in the hull. The result should be a donut of teak that fits over the thru hull and goes all the way down to touch the hull. Now take off the donut and screw on the sea cock and count the turns until it seats. Unscrew and try it with the donut in place. Cut down the donut until the thru hull engages almost all of its threads. When you have the donut cut to size give it a coat of penetrating epoxy then a coat of regular epoxy following the instructions. You can buy small epoxy kits at West Marine that should be just enough to do all of the thru hulls on a Cat 27. For final assembly glue the donut to the hull with 4200 and attache the sea cock with plenty of teflon tape. For security I drilled a pilot hole and used a 3/4" stainless lag screw to attach the thru hull flange to the donut. Don't drill right through the hull when drilling the pilot hole. You will have to buy and install a tail piece with pipe threads on one end and a hose barb on the other. Use plenty of teflon tape here too. Attach the hose using double hose clamps and consider replacing the old hose at this time. Once I figured out what was what I did the engine intake (replacing the scoop strainer thru hull) and the sink/ice box thru hull in about an hour for each. I have photos and I will put them in the photo gallery soon.
M
Michael McCann
G
Gene
J
John Visser
Great!
What a great note! This is really useful, helpful info. Here is a link to another explanation, with some interesting differences. I am interested in your view as to the differences. jv
What a great note! This is really useful, helpful info. Here is a link to another explanation, with some interesting differences. I am interested in your view as to the differences. jv
G
Gene
Revision??
John, Really like these instructions. Wondered about using the seacock as a lock nut for the thru hull, but it does make the installation easier and more ridge. Can't think of any circumstances where not using the orginal thru hull lock would be detrimental. Onlt thing I don't like about the article is having the bolts go through the hull. Think I will epoxy the plywood to the hull and use stubby screws into the plywood to keep the seacock from turning but don't penetrate the hull. Gene
John, Really like these instructions. Wondered about using the seacock as a lock nut for the thru hull, but it does make the installation easier and more ridge. Can't think of any circumstances where not using the orginal thru hull lock would be detrimental. Onlt thing I don't like about the article is having the bolts go through the hull. Think I will epoxy the plywood to the hull and use stubby screws into the plywood to keep the seacock from turning but don't penetrate the hull. Gene
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