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  1. #1

    Replacing main engine seacocks

    I am looking for the size of the thru hulls and seacocks on the main engines on my 1969 45c it has 8-71 naturals. I plan on replacing them in the next few weeks. I would also appreciate any advice on the job also. Thanks in advance.
    Last edited by Seapig100; 05-04-2019 at 02:09 PM.

  2. #2

    Re: Replacing main engine seacocks

    Probably two inches to three inches. Use Groco, Conbraco or Apollo. Use made in USA, no import stuff. Backing plates and through-bolting the flanges is very important/. Use 4200 to seal. Be aware of the difference between NPT and NPS threads and don't mix them. The right ones are cast silicon bronze with stainless ball valves. If you want to fit a strainer, it should be separate and supported sturdily; you will need a lot of bronze hose barbs to hook up all the hoses. Double clamp everything with AWAB clamps. Use the best hose you can buy, I have found Vetus to be the best so far.

  3. #3

    Re: Replacing main engine seacocks

    Thank you.

  4. #4

    Re: Replacing main engine seacocks

    Why are you replacing them?
    ENUFF. 1983 53MY.Hull #617 Barnegat Light Nj.

  5. #5

    Re: Replacing main engine seacocks

    They are frozen open and I have made several attempts to get them moving again with no luck. I am planning on storing in the water next winter and I need all my seacocks to be in good working order. There are no sea strainers on the mains and I would like to do this at the same time. And last but certainly not least the plumbing from the seacocks to the engines is not up to marine standards and it bothers me every time I look at it. There is copper tubing attaching the seacock to the hose and copper tubing being used to create a 90 degree bend. And all this is in 4 inch hose to accommodate the tubing. The fittings at the engine is smaller so the previous owner just clamped down the hose to fit the engine and that is stressing the hose.I figure it’s going to cost me about 3500 bucks to change all the seacocks, IMO it’s money well spent.

  6. #6

    Re: Replacing main engine seacocks

    Frozen seacocks are common. My boat surveyed frozen main seacocks. They now open and close with just a finger or two. I was able to bring mine back in the water. You may not want to try. But if you do, I’ll be glad to explain what worked for me.
    Semper Siesta
    Robert Clarkson
    ASLAN, 1983 55C #343
    Charleston, SC

  7. #7

    Re: Replacing main engine seacocks

    Quote Originally Posted by Seapig100 View Post
    They are frozen open and I have made several attempts to get them moving again with no luck. I am planning on storing in the water next winter and I need all my seacocks to be in good working order. There are no sea strainers on the mains and I would like to do this at the same time. And last but certainly not least the plumbing from the seacocks to the engines is not up to marine standards and it bothers me every time I look at it. There is copper tubing attaching the seacock to the hose and copper tubing being used to create a 90 degree bend. And all this is in 4 inch hose to accommodate the tubing. The fittings at the engine is smaller so the previous owner just clamped down the hose to fit the engine and that is stressing the hose.I figure it’s going to cost me about 3500 bucks to change all the seacocks, IMO it’s money well spent.
    Sounds like you are doing this work for all the right reasons. As RAC said, you might be able to get the current ones moving, which solves part of the problem. You would still need to correct all the plumbing, as you pointed out. That may turn out to be the main issue if you can get the sea valves to open and close. You may not need to replace them.

    If you look at some of RACs posts on his engine room, you will get an idea of the quality of work he expects from himself and on his boat. I would feel safe taking his suggestions.

    The best source I have found for this kind of hardware is Groco here in MD. (now, part of this is that they are local to me and they make everything here in the USA, although their actual foundry is in PA- but it isn't overseas) Their ARG series strainers are very good. I have several of them and they are very good about keeping spares and gaskets etc for all their products, old and new, in stock. I have a Groco FW system pump, for example, that probably has fifteen years on it, now.

  8. Re: Replacing main engine seacocks

    This type.
    seacock.jpg

  9. #9

    Re: Replacing main engine seacocks

    Quote Originally Posted by jim rosenthal View Post
    Sounds like you are doing this work for all the right reasons. As RAC said, you might be able to get the current ones moving, which solves part of the problem. You would still need to correct all the plumbing, as you pointed out. That may turn out to be the main issue if you can get the sea valves to open and close. You may not need to replace them.

    If you look at some of RACs posts on his engine room, you will get an idea of the quality of work he expects from himself and on his boat. I would feel safe taking his suggestions.

    The best source I have found for this kind of hardware is Groco here in MD. (now, part of this is that they are local to me and they make everything here in the USA, although their actual foundry is in PA- but it isn't overseas) Their ARG series strainers are very good. I have several of them and they are very good about keeping spares and gaskets etc for all their products, old and new, in stock. I have a Groco FW system pump, for example, that probably has fifteen years on it, now.
    Jim, thanks for the kind words. Let me address the post and your PM together here.

    First, freeing a stuck seacock won't be fast. But it is a lot cheaper than replacements.

    Spray penetrating oil on the valve assembly copiously and often--maybe every time you pass by for days. Also spray oil on the freeze/drain plug. Also, disconnect the hose from the seacock to the pump at the pump. Stuff a rag down the hose until you feel it at the seacock. Pour in full concentrate phosphoric acid or CLR. The rag helps stem the flow of the acid out the open seacock. Let this stand, and continually refresh solution. Continue oiling valve assembly. As an alternative, a diver can remove the screen and stuff the intake which is a good route. But you may not be able to fully close the seacock until the intake is cleared.

    If necessary, make a cheater about a foot in length. Being careful not to round off the valve stem, work the handle back and forth. It may not move for the first few tries (or days). But, most of what you're doing doesn't take much time at any one session. Use a brass hammer and whack the assembly pretty good at anytime during the process. I thought an orbital sandy was a useful tool on helping to free things up.

    After a time, the seacock will move back and forth a bit. Don't trying force it. Using a coat hanger, pull the rag out. Now, you can use a torch and heat the seacock. It's pretty massive, so you shouldn't worry about melting your boat. Work the heat all around the body; it'll take a while. Go the whip (hammer). You can wet the base of the seacock and watch for signs of heat rapidly evaporating the moisture as a safety check. Re-oil when it cools down.

    Once the seacock is about halfway closed, remove the freeze plug and screw in a zerk fitting. Shoot some grease in the assembly. Most of the grease will go in the water until the seacock is completely closed. Then, grease it well.

    Also, once the seacock is closed, add CLR or about a 50/50 mix of phosphoric and let stand overnight. I think you will be surprised at how easy the valve will open and close after a day or two. Exercise regularly and it should become lighter and lighter to the touch.

    Seems like a lot of work, but it's really just a couple of hours total spread over time. Good luck.
    Semper Siesta
    Robert Clarkson
    ASLAN, 1983 55C #343
    Charleston, SC

  10. #10

    Re: Replacing main engine seacocks

    I was able to spin new valves on my existing thru hulls saved a lot of money and time.
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    43DCFB DC-306
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