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Author Topic:   Patching screw holes in bilge

Frank O posted 03-03-2012 11:54 PM ET (US)
When I went to install a new float switch for my bilge pump today, I noticed a few screws dotted around the floor of the bilge. I gather that when float switches were replaced previously, instead of removing screws and patching the holes, the screws were left in place with a generous dollop of 3M 5200. Some of these will get in the way of my new float switch, though, so it's time for repairs.
From reviewing old threads here, I gather the drill is to fill the holes with an epoxy (West System and Marine-Tex each having their adherents). In theory I could finish with gelcoat, but I'm not sure this helps in the bilge (I gather gelcoat's main function is to prevent damage from ultraviolet light?), and aesthetics are not important.
But it is important to make sure the holes are well-sealed, since there will often be a small amount of standing water that the pump doesn't remove. For average small screw holes, would you just inject the epoxy and call it a day, or prep the holes by, say, chamfering them out a bit with a drill or Dremel tool?

tom976 posted 03-05-2012 10:17 AM ET (US)
I would do it one of two ways....
Marinetex works great. You mix that up, get a nice pointy syringe. Clean out the area, make it dry as can be. Get any loose wood inside that hole out. You take the syringe fill it up and inject it from the inside out so no air pockets are in there. (voids are never good)
Others would do the same method with using gelcoat in there and injecting from the inside to the out.
contender posted 03-05-2012 12:41 PM ET (US)
Almost what Tom has stated, I would drill out the holes to a larger size 5/16-3/8 (cleans the loose and wet sides) blow them out to dry them (compressor), then make either a fiberglass paste, or a good epoxy to fill them with. Use the syringe to have no air voids...
Frank O posted 03-05-2012 05:20 PM ET (US)
Thanks, sounds like good advice.
Two more questions:
1) For the new screws I'll be putting in the floor of the bilge, would you seal them with Marine-Tex? Or 5200?
2) I'm not planning to move the pump itself from its existing position. The bracket it snaps into has been there for many years. Would it be desirable to remove its screws and reseal them (with whatever you recommend in question 1)? Or leave well enough alone?
acseatsri posted 03-05-2012 06:54 PM ET (US)
I would just use 5200 to seal them in that area. Marine-tex is really not a sealant but more an epoxy paste. 5200 is recommended for use below the waterline, is messy and sticks to everything - which is why it's such a good product.
Of more importance would be to check the integrity of the drain tubes and how well they're sealed.
Owtrayj25 posted 03-05-2012 08:26 PM ET (US)
I would not use 3M 5200 to address the filling of open screw holes. 3m 5200 is an adhesive and as such it's recommended uses are primarily for joining 2 materials together, or sealing the joints of materials mechanically joined.
The proper fix for unused screw holes would be to ream out the hole, chamfer the edges and fill the hole from the bottom up with either epoxy or polyester resin. If you are anal, you can fair the area with the adjoining surface.
Frank O posted 03-05-2012 10:43 PM ET (US)
Thanks. Owtrayj25, just to clarify, I wouldn't consider using 5200 to fill open screw holes. My last question was whether it would be preferable to epoxy to seal around a screw going into a new hole (evidently yes).
Owtrayj25 posted 03-06-2012 08:38 AM ET (US)
Once you have drilled your new holes for the bilge pump, fill the holes and coat the screws with Boatlife "lifeseal" sealant.
David Pendleton posted 03-06-2012 05:11 PM ET (US)
I have a similar repair to make this spring, but when I drill out the existing hole I'll be drilling directly into the foam.
Will an epoxy like West System bond with the polyurethane foam?
KDW posted 03-06-2012 05:23 PM ET (US)
For small holes 1/4" and less in diameter, I've used 3M 5200 for years to fill alot of holes in several whalers above and below the water line. It hasn't let me down yet. Also works well as a second coat around the drain tube flanges - just in case.
It may not be the text book method, but works good enough for me and I would trust 3M 5200 for sealing small holes more than Marine Tex.
KW
Theron1033 posted 03-10-2012 01:59 AM ET (US)
I've seen this before, were people install float switches in their whaler and end up screwing them through the glass and into the foam. BIG PROBLEM, no matter how much 5200 you seal it with after a while the 5200 will disintegrate and loose it's seal, allowing water to enter into the foam, and we all know those bilge holes in whalers always have water in them, you are looking at potential water log and foam rot. i would highly suggest otherwise to screwing your float switch into your hull
L H G posted 03-10-2012 01:09 PM ET (US)
Old bilge pump screws (usually #8 or #10 size) in sump and bilge areas are difficult to work in, to fill, sand out, and gelcoat over, and rarely seen. If I was going to attempt it, I would use Evercoat Fromula 27, a polyester resin which can receive gelcoat cover.
But I don't do that. If nothing will sit flush on top of the hole, I fill with Life Seal (rated for underwater use) and install a same size 3/4" pan head screw as long as the threads in the glass are not stripped out. I leave the sealant that oozes out around and under the screw head in place. If something has to sit over the hole and I need a flush surface, I grind a countersink bevel to receive a flat head screw set the same way.
I have used this method for years, with never a problem or wet foam under sump. The screw tightly threaded into the glass skin, along with the sealant, makes it waterproof.
acseatsri posted 03-10-2012 05:35 PM ET (US)
""I would not use 3M 5200 to address the filling of open screw holes. 3m 5200 is an adhesive and as such it's recommended uses are primarily for joining 2 materials together, or sealing the joints of materials mechanically joined.""
That's weird. The tube I have in my hand now says "adhesive sealant". Your tube must be different than mine.
I've used it on screw holes and sealing screws, including transducers and drain tubes, for years without adverse effects, including the product disintegrating.
About the only thing I wouldn't use it for is caulking deck seams. For that I use Boatlife caulk.
davej14 posted 03-11-2012 01:57 PM ET (US)
I would do the same as LHG but in your case chamfer the hole and use stainless flat head screws with boatlife caulk to fill them. Nothing will stick up in the way of your new installation. Epoxy may not bond well if the area is damp while boat life caulk will set up better with a little moisture.
Owtrayj25 posted 03-12-2012 07:29 AM ET (US)

quote:
That's weird. The tube I have in my hand now says "adhesive sealant". Your tube must be different than mine.
No, my tube also says "adhesive sealant", so it is the same as yours. What is interesting though is that all of the sealant applications listed on the 3M website, not once mentioned is to use the product as a fill material for old screw holes, or and type of filling voids for that matter. Probably because 3M knows when filling voids, even small ones, should be done from the bottom up, which is nearly impossible with such a large discharge tube. Here is what 3M recommends as "sealant" applications
Applications
• Thru Hulls
• Hatches
• Rub Rails
• Hinges
• Door Flanges
• Trim
• Porthole Frames
• Trunk Joints
• Struts & Planking
• Stern Joints
• Slip Rails
• Electrical Assemblies
• Port Lights
In each case, we see that 5200 is recommended when joining or sealing 2 materials together. In order to fill a screw hole correctly with 5200, you would have to transfer the adhesive to a much smaller syringe so the material could be filled from the bottom up. Knowing the characteristics of 5200, this would be quite a messy process. Squirting a little on the top of the screw hole and trying to push it down into a hole is a poor way of filling any void correctly.

KDW posted 03-12-2012 12:49 PM ET (US)
Not sure anyone is advocating drilling new holes to mount a float switch. Only what to do with holes that are already there.
A small tooth pick or tie wrap does fine to work the 5200 down and around inside a screw hole....no biggie.
If someone has used 5200 and had problems filling small holes, then I'd like to hear from them. Everything else is pure speculation on it's failure as a good sealant in this application. I stand by my experience and have used 5200 on many small holes above and below the water line, including handrail stantions and such for years.....it helps keep screws from backing out and of course keeps moisture and water out.
KW
Frank O posted 03-13-2012 01:13 PM ET (US)
If none of the existing holes are in a suitable place, what would be the preferred way to mount a new float switch?
jimh posted 03-14-2012 08:25 AM ET (US)
I give some very important advice to consider in mounting the float switch in an article at
http://continuouswave.com/whaler/reference/bilgePump.html
See the material under the subheading "Location of Float Switch."
jimh posted 03-14-2012 08:35 AM ET (US)
Larry's method of using a screw fastener to fill an old screw fastener hole is a good method of providing a pleasant appearance to the empty screw fastener hole, and I have used that method myself to fill some no longer needed holes in the deck and coaming of my boat. An exposed flat head screw with dress washer does not look out of place and is often more attractive than a badly done resin patch. In the bilge sump I do not think appearances are overly important, and since the bilge sump is inherently a wet area, it is not a good place for metal, even stainless steel, as a filler material. On that basis I would omit the new screw as a filler in an old hole.
My method for filling an unneeded screw fastener hole in the sump compartment is to use a thickened epoxy. A good boat caulk will also be a proper sealant. You do not need to impart any structural strength to the repair of a small screw hole; you just want to keep water from entering into the foam of the Unibond hull.
Frank O posted 03-15-2012 08:46 PM ET (US)
Jim, your article has some very helpful information. However, I don't think it addresses the specific point I was trying to get at. When installing a new float switch, Theron1033 said it would be highly desirable *not* to use screws. My question is, if you don't hold it down with screws, how do you secure it?
jimh posted 03-15-2012 09:50 PM ET (US)
Frank--I don't understand why fastening the float switch in place with two or three small stainless steel self-tapping screws would not be a good method. That is the method that Boston Whaler uses, and, as best as I can recall, that is the method I have seen every other boat builder use to install the float switch. If the screw fasteners are properly bedded in a sealant there should not be concern about water intrusion into the interior of the Unibond hull.
In the absence of a mechanical fastener like a self-tapping screw, the only alternative I can imagine is to use a strong adhesive. The problem with adhesives is that they tend to be a one-time-use approach to bonding. If the adhesive is strong enough to hold the float switch in place in all the rough motion and pounding you get in a boat, it will probably be too strong to easily remove the float switch when the float switch fails and needs replacement.

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Author	Topic: Patching screw holes in bilge
Frank O	posted 03-03-2012 11:54 PM ET (US) When I went to install a new float switch for my bilge pump today, I noticed a few screws dotted around the floor of the bilge. I gather that when float switches were replaced previously, instead of removing screws and patching the holes, the screws were left in place with a generous dollop of 3M 5200. Some of these will get in the way of my new float switch, though, so it's time for repairs. From reviewing old threads here, I gather the drill is to fill the holes with an epoxy (West System and Marine-Tex each having their adherents). In theory I could finish with gelcoat, but I'm not sure this helps in the bilge (I gather gelcoat's main function is to prevent damage from ultraviolet light?), and aesthetics are not important. But it is important to make sure the holes are well-sealed, since there will often be a small amount of standing water that the pump doesn't remove. For average small screw holes, would you just inject the epoxy and call it a day, or prep the holes by, say, chamfering them out a bit with a drill or Dremel tool?
tom976	posted 03-05-2012 10:17 AM ET (US) I would do it one of two ways.... Marinetex works great. You mix that up, get a nice pointy syringe. Clean out the area, make it dry as can be. Get any loose wood inside that hole out. You take the syringe fill it up and inject it from the inside out so no air pockets are in there. (voids are never good) Others would do the same method with using gelcoat in there and injecting from the inside to the out.
contender	posted 03-05-2012 12:41 PM ET (US) Almost what Tom has stated, I would drill out the holes to a larger size 5/16-3/8 (cleans the loose and wet sides) blow them out to dry them (compressor), then make either a fiberglass paste, or a good epoxy to fill them with. Use the syringe to have no air voids...
Frank O	posted 03-05-2012 05:20 PM ET (US) Thanks, sounds like good advice. Two more questions: 1) For the new screws I'll be putting in the floor of the bilge, would you seal them with Marine-Tex? Or 5200? 2) I'm not planning to move the pump itself from its existing position. The bracket it snaps into has been there for many years. Would it be desirable to remove its screws and reseal them (with whatever you recommend in question 1)? Or leave well enough alone?
acseatsri	posted 03-05-2012 06:54 PM ET (US) I would just use 5200 to seal them in that area. Marine-tex is really not a sealant but more an epoxy paste. 5200 is recommended for use below the waterline, is messy and sticks to everything - which is why it's such a good product. Of more importance would be to check the integrity of the drain tubes and how well they're sealed.
Owtrayj25	posted 03-05-2012 08:26 PM ET (US) I would not use 3M 5200 to address the filling of open screw holes. 3m 5200 is an adhesive and as such it's recommended uses are primarily for joining 2 materials together, or sealing the joints of materials mechanically joined. The proper fix for unused screw holes would be to ream out the hole, chamfer the edges and fill the hole from the bottom up with either epoxy or polyester resin. If you are anal, you can fair the area with the adjoining surface.
Frank O	posted 03-05-2012 10:43 PM ET (US) Thanks. Owtrayj25, just to clarify, I wouldn't consider using 5200 to fill open screw holes. My last question was whether it would be preferable to epoxy to seal around a screw going into a new hole (evidently yes).
Owtrayj25	posted 03-06-2012 08:38 AM ET (US) Once you have drilled your new holes for the bilge pump, fill the holes and coat the screws with Boatlife "lifeseal" sealant.
David Pendleton	posted 03-06-2012 05:11 PM ET (US) I have a similar repair to make this spring, but when I drill out the existing hole I'll be drilling directly into the foam. Will an epoxy like West System bond with the polyurethane foam?
KDW	posted 03-06-2012 05:23 PM ET (US) For small holes 1/4" and less in diameter, I've used 3M 5200 for years to fill alot of holes in several whalers above and below the water line. It hasn't let me down yet. Also works well as a second coat around the drain tube flanges - just in case. It may not be the text book method, but works good enough for me and I would trust 3M 5200 for sealing small holes more than Marine Tex. KW
Theron1033	posted 03-10-2012 01:59 AM ET (US) I've seen this before, were people install float switches in their whaler and end up screwing them through the glass and into the foam. BIG PROBLEM, no matter how much 5200 you seal it with after a while the 5200 will disintegrate and loose it's seal, allowing water to enter into the foam, and we all know those bilge holes in whalers always have water in them, you are looking at potential water log and foam rot. i would highly suggest otherwise to screwing your float switch into your hull
L H G	posted 03-10-2012 01:09 PM ET (US) Old bilge pump screws (usually #8 or #10 size) in sump and bilge areas are difficult to work in, to fill, sand out, and gelcoat over, and rarely seen. If I was going to attempt it, I would use Evercoat Fromula 27, a polyester resin which can receive gelcoat cover. But I don't do that. If nothing will sit flush on top of the hole, I fill with Life Seal (rated for underwater use) and install a same size 3/4" pan head screw as long as the threads in the glass are not stripped out. I leave the sealant that oozes out around and under the screw head in place. If something has to sit over the hole and I need a flush surface, I grind a countersink bevel to receive a flat head screw set the same way. I have used this method for years, with never a problem or wet foam under sump. The screw tightly threaded into the glass skin, along with the sealant, makes it waterproof.
acseatsri	posted 03-10-2012 05:35 PM ET (US) ""I would not use 3M 5200 to address the filling of open screw holes. 3m 5200 is an adhesive and as such it's recommended uses are primarily for joining 2 materials together, or sealing the joints of materials mechanically joined."" That's weird. The tube I have in my hand now says "adhesive sealant". Your tube must be different than mine. I've used it on screw holes and sealing screws, including transducers and drain tubes, for years without adverse effects, including the product disintegrating. About the only thing I wouldn't use it for is caulking deck seams. For that I use Boatlife caulk.
davej14	posted 03-11-2012 01:57 PM ET (US) I would do the same as LHG but in your case chamfer the hole and use stainless flat head screws with boatlife caulk to fill them. Nothing will stick up in the way of your new installation. Epoxy may not bond well if the area is damp while boat life caulk will set up better with a little moisture.
Owtrayj25	posted 03-12-2012 07:29 AM ET (US) quote: That's weird. The tube I have in my hand now says "adhesive sealant". Your tube must be different than mine. No, my tube also says "adhesive sealant", so it is the same as yours. What is interesting though is that all of the sealant applications listed on the 3M website, not once mentioned is to use the product as a fill material for old screw holes, or and type of filling voids for that matter. Probably because 3M knows when filling voids, even small ones, should be done from the bottom up, which is nearly impossible with such a large discharge tube. Here is what 3M recommends as "sealant" applications Applications • Thru Hulls • Hatches • Rub Rails • Hinges • Door Flanges • Trim • Porthole Frames • Trunk Joints • Struts & Planking • Stern Joints • Slip Rails • Electrical Assemblies • Port Lights In each case, we see that 5200 is recommended when joining or sealing 2 materials together. In order to fill a screw hole correctly with 5200, you would have to transfer the adhesive to a much smaller syringe so the material could be filled from the bottom up. Knowing the characteristics of 5200, this would be quite a messy process. Squirting a little on the top of the screw hole and trying to push it down into a hole is a poor way of filling any void correctly.
KDW	posted 03-12-2012 12:49 PM ET (US) Not sure anyone is advocating drilling new holes to mount a float switch. Only what to do with holes that are already there. A small tooth pick or tie wrap does fine to work the 5200 down and around inside a screw hole....no biggie. If someone has used 5200 and had problems filling small holes, then I'd like to hear from them. Everything else is pure speculation on it's failure as a good sealant in this application. I stand by my experience and have used 5200 on many small holes above and below the water line, including handrail stantions and such for years.....it helps keep screws from backing out and of course keeps moisture and water out. KW
Frank O	posted 03-13-2012 01:13 PM ET (US) If none of the existing holes are in a suitable place, what would be the preferred way to mount a new float switch?
jimh	posted 03-14-2012 08:25 AM ET (US) I give some very important advice to consider in mounting the float switch in an article at http://continuouswave.com/whaler/reference/bilgePump.html See the material under the subheading "Location of Float Switch."
jimh	posted 03-14-2012 08:35 AM ET (US) Larry's method of using a screw fastener to fill an old screw fastener hole is a good method of providing a pleasant appearance to the empty screw fastener hole, and I have used that method myself to fill some no longer needed holes in the deck and coaming of my boat. An exposed flat head screw with dress washer does not look out of place and is often more attractive than a badly done resin patch. In the bilge sump I do not think appearances are overly important, and since the bilge sump is inherently a wet area, it is not a good place for metal, even stainless steel, as a filler material. On that basis I would omit the new screw as a filler in an old hole. My method for filling an unneeded screw fastener hole in the sump compartment is to use a thickened epoxy. A good boat caulk will also be a proper sealant. You do not need to impart any structural strength to the repair of a small screw hole; you just want to keep water from entering into the foam of the Unibond hull.
Frank O	posted 03-15-2012 08:46 PM ET (US) Jim, your article has some very helpful information. However, I don't think it addresses the specific point I was trying to get at. When installing a new float switch, Theron1033 said it would be highly desirable not to use screws. My question is, if you don't hold it down with screws, how do you secure it?
jimh	posted 03-15-2012 09:50 PM ET (US) Frank--I don't understand why fastening the float switch in place with two or three small stainless steel self-tapping screws would not be a good method. That is the method that Boston Whaler uses, and, as best as I can recall, that is the method I have seen every other boat builder use to install the float switch. If the screw fasteners are properly bedded in a sealant there should not be concern about water intrusion into the interior of the Unibond hull. In the absence of a mechanical fastener like a self-tapping screw, the only alternative I can imagine is to use a strong adhesive. The problem with adhesives is that they tend to be a one-time-use approach to bonding. If the adhesive is strong enough to hold the float switch in place in all the rough motion and pounding you get in a boat, it will probably be too strong to easily remove the float switch when the float switch fails and needs replacement.