I have recently been advised to replace all through hull fittings on my '87 Catalina 36 as precautionary maintenance. I recently painted the bottom and no damage was noted in the through hull fittings at that time...I think that the main concern is that the fittings are plastic and not brass. I am under the impression that these fittings do not need to be routinely replaced unless damaged. Does anyone out there have any experience with this type of situation...thanks, dick
Plastic Through Hull Replacement
- Thread starter Hookem
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looking for work
Hi Rich - Sounds like a yard is fishing for work. My experience with my 1986 C36 is that the thru hulls last a long time. They definitely need routine inspection and excercise (work them periodically), but you don't need to replace them if they are functioning properly. Trevor
Hi Rich - Sounds like a yard is fishing for work. My experience with my 1986 C36 is that the thru hulls last a long time. They definitely need routine inspection and excercise (work them periodically), but you don't need to replace them if they are functioning properly. Trevor
They're NOT plastic
Richard They're marelon, made by Forespar. Look at the link from the archives. Stu
Richard They're marelon, made by Forespar. Look at the link from the archives. Stu
Confusion of terms here
Are we talking about thru-hulls or seacocks? A thru-hull is a pipe that goes through the hull to let water in or out. A seacock is a valve on top of a thru-hull to allow such same water to enter or exit the vessel at a time appropriate for the skipper’s needs by opening the valve in such seacock. The skipper closes such same valve to disallow water from entering or exiting the vessel. It appears from Richard’s description of examining the thru-hull from the outside of the hull, that he is referring to the former and not a seacock as the two earlier responses seem to imply. I am quite certain the exterior body of a seacock can only be examined from inside a vessel. Nevertheless, probably two issues here are of concern to Richard. The first is the possibility of a bronze seacock on a brass thru-hull. This is significant, as there is electrolysis between the brass and bronze. This electrolysis tends to eat away at the bronze valve. The valve will fail and leak badly enough to sink the vessel. Hence, Richard needs to determine positively of what material the thru-hull is constructed. The three most common materials are brass, bronze, and plastic. As both bronze and brass have poor magnetic properties, potentially the only fashion to determine if the thru-hull is either plastic or metal, would be to try a small scrape along the thru-hull with a knife or hack saw blade which should demonstrate if the thru-hull is plastic or metal. If it appears from this process that the thru-hull is plastic, then a bronze seacock can be successfully attached to the thru-hull without concern of electrolysis. If it appears from this process that the thru-hull is metal, then there is the difficult task of establishing whether it is bronze or brass. Generally, brass parts are “stamped” or smooth while bronze parts are “cast” and have a rough surface from the sand molds. Note this is a very general description. Further, bronze may be machined sufficiently to where it appears smooth and hence is mistaken for brass. Hence, if the thru-hull is metal, it is best to use a “plastic” or Marlon seacock on the thru-hull to eliminate the electrolysis from placing a bronze seacock onto a brass thru-hull. Now, the second issue of concern to Richard is the propensity for Marlon valve handles to suddenly break off. Hence, some sailors state that only bronze seacocks should be employed as the Marlon seacock handles break too easily. However, as mentioned earlier, bronze seacocks may only be placed onto bronze or plastic thru-hulls. So, if one wishes to use a bronze seacock on a metal thru-hull that one does not know with absolute certainty is constructed of bronze, one should replace the thru-hull with a thru-hull that one knows is constructed of bronze. However, replacing a perfectly good thru-hull is probably not wise action for if the new thru-hull leaks, then the vessel must be hauled so that the thru hull can be tightened by holding it from the outside while its nut is turned from the inside. (You might be able to do it holding the seacock, but as everything is a right hand thread, you will probably find that this does not work.) Thusly, unless they are damaged or leaking, thru-hulls are best left alone, and the seacock is replaced. Hence, we are back to seacocks. If Richard establishes that he has a metal thru-hull and cannot determine with absolute certainty that the thru-hull is bronze, he must use a Marlon seacock. Nevertheless, the well experienced broken handle weakness of Marlon seacocks is significantly mitigated through good maintenance of the valve by regular greasing of the ball valve and turning of the handle. On my Marlon valves, I use Super Lube (yellow cap) that I spray it onto the closed valve from below up through the thru-hull and then down from the top of the seacock. This is performed twice a season, once in the spring before launch, and then after haul out in the fall. Super Lube (yellow cap) is synthetic and does not contain any petroleum distillates that may react poorly with the materials of the Marlon seacock. There are other methods to grease these Marlon seacocks; my particular method seems to be the most convenient for me. I turn the handles at least once a week during the summer. I also try to turn the handles on warm days during the winter, but I do not always do that. My four Marlon seacocks have been on my boat for twelve years, and I have not broken any of their handles up to this point.
Are we talking about thru-hulls or seacocks? A thru-hull is a pipe that goes through the hull to let water in or out. A seacock is a valve on top of a thru-hull to allow such same water to enter or exit the vessel at a time appropriate for the skipper’s needs by opening the valve in such seacock. The skipper closes such same valve to disallow water from entering or exiting the vessel. It appears from Richard’s description of examining the thru-hull from the outside of the hull, that he is referring to the former and not a seacock as the two earlier responses seem to imply. I am quite certain the exterior body of a seacock can only be examined from inside a vessel. Nevertheless, probably two issues here are of concern to Richard. The first is the possibility of a bronze seacock on a brass thru-hull. This is significant, as there is electrolysis between the brass and bronze. This electrolysis tends to eat away at the bronze valve. The valve will fail and leak badly enough to sink the vessel. Hence, Richard needs to determine positively of what material the thru-hull is constructed. The three most common materials are brass, bronze, and plastic. As both bronze and brass have poor magnetic properties, potentially the only fashion to determine if the thru-hull is either plastic or metal, would be to try a small scrape along the thru-hull with a knife or hack saw blade which should demonstrate if the thru-hull is plastic or metal. If it appears from this process that the thru-hull is plastic, then a bronze seacock can be successfully attached to the thru-hull without concern of electrolysis. If it appears from this process that the thru-hull is metal, then there is the difficult task of establishing whether it is bronze or brass. Generally, brass parts are “stamped” or smooth while bronze parts are “cast” and have a rough surface from the sand molds. Note this is a very general description. Further, bronze may be machined sufficiently to where it appears smooth and hence is mistaken for brass. Hence, if the thru-hull is metal, it is best to use a “plastic” or Marlon seacock on the thru-hull to eliminate the electrolysis from placing a bronze seacock onto a brass thru-hull. Now, the second issue of concern to Richard is the propensity for Marlon valve handles to suddenly break off. Hence, some sailors state that only bronze seacocks should be employed as the Marlon seacock handles break too easily. However, as mentioned earlier, bronze seacocks may only be placed onto bronze or plastic thru-hulls. So, if one wishes to use a bronze seacock on a metal thru-hull that one does not know with absolute certainty is constructed of bronze, one should replace the thru-hull with a thru-hull that one knows is constructed of bronze. However, replacing a perfectly good thru-hull is probably not wise action for if the new thru-hull leaks, then the vessel must be hauled so that the thru hull can be tightened by holding it from the outside while its nut is turned from the inside. (You might be able to do it holding the seacock, but as everything is a right hand thread, you will probably find that this does not work.) Thusly, unless they are damaged or leaking, thru-hulls are best left alone, and the seacock is replaced. Hence, we are back to seacocks. If Richard establishes that he has a metal thru-hull and cannot determine with absolute certainty that the thru-hull is bronze, he must use a Marlon seacock. Nevertheless, the well experienced broken handle weakness of Marlon seacocks is significantly mitigated through good maintenance of the valve by regular greasing of the ball valve and turning of the handle. On my Marlon valves, I use Super Lube (yellow cap) that I spray it onto the closed valve from below up through the thru-hull and then down from the top of the seacock. This is performed twice a season, once in the spring before launch, and then after haul out in the fall. Super Lube (yellow cap) is synthetic and does not contain any petroleum distillates that may react poorly with the materials of the Marlon seacock. There are other methods to grease these Marlon seacocks; my particular method seems to be the most convenient for me. I turn the handles at least once a week during the summer. I also try to turn the handles on warm days during the winter, but I do not always do that. My four Marlon seacocks have been on my boat for twelve years, and I have not broken any of their handles up to this point.
Marelon Thru-Hulls/SeaCocks
They require regular attention, just like anything else on a boat. 1. Regularly "exercise them" by opening/closing the sea cocks once or twice a week. 2. Regularly lubricate them with a non-petroleum waterproof grease (e.g., SuperLube) at least twice a year. After haulout & prior to launch is probably OK. Keep some wooden plugs & a mallet handy in case one fails (regardless of the material it's made from). --RonD
They require regular attention, just like anything else on a boat. 1. Regularly "exercise them" by opening/closing the sea cocks once or twice a week. 2. Regularly lubricate them with a non-petroleum waterproof grease (e.g., SuperLube) at least twice a year. After haulout & prior to launch is probably OK. Keep some wooden plugs & a mallet handy in case one fails (regardless of the material it's made from). --RonD
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