Filling screw holes in hull

Jun 11, 2004
1,621
Oday 31 Redondo Beach
I need to fill a couple of #10 screw holes from an old thru hull strainer for an engine intake (changing to a new pattern strainer). The holes do not penetrate all the way through the hull. Should I fill them with epoxy or a sealant like Sikaflex? I have heard that it is sometimes good to put a screw in the old hole and leave it there. Is that a good idea?

Thanks.
 
Oct 22, 2014
20,995
CAL 35 Cruiser #21 moored EVERETT WA
Small holes... Thickened Epoxy. sand back fair the surface, then cover with primer and barrier coat. Then you can paint.
Screws in the hole just give you something to catch on, rip out, or rust out. Not on my boat.
 
Jun 11, 2004
1,621
Oday 31 Redondo Beach
Small holes... Thickened Epoxy. sand back fair the surface, then cover with primer and barrier coat. Then you can paint.
Screws in the hole just give you something to catch on, rip out, or rust out. Not on my boat.
Thanks, Now as I recall that screw in the hole idea was for metal spars not fiberglass.
 
  • Like
Likes: jssailem
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
Another vote for thickened epoxy. Before injecting the epoxy clean out the hole with a drill bit one size larger than the existing hole, this will remove any crud and bedding compound in the hole and give the epoxy a cleaner surface to adhere to. Becarefull that you don't drill all the way through the hull! :yikes: A hand drill might give you better control of the depth and how much material you are removing.
 
Mar 26, 2017
32
Irwin 38 Palacios
I recently used 2 part J & B weld epoxy to fill 4 screw holes in my bilge worked great!
 
Mar 23, 2015
259
Catalina 22 MK-II Dillon, CO
Same question, but in gelcoat. As I understand it, gelcoat won't adhere to the epoxy. In this case, should the hole be filled with gelcoat as well? I have several holes in the transom from an old transducer.
 

Ward H

.
Nov 7, 2011
3,645
Catalina 30 Mk II Barnegat, NJ
In the transom above the water line I just left machine screws, sealed with butyl tape, in any holes. I think that looks better than dealing with any ugly spots from mismatched gel coat.
Under water, thickened epoxy as the others have said.
 
Jan 19, 2010
12,362
Hobie 16 & Rhodes 22 Skeeter Charleston
If it is in an obscure place, after filling the holes, I'd cover with one or two layers of fiberglass cloth.
 
Mar 23, 2015
259
Catalina 22 MK-II Dillon, CO
On the transom. Some of the holes go through. So I think I'll fill the holes with epoxy, with a slight divet and then finish with gelcoat. Make sense?
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
On the transom. Some of the holes go through. So I think I'll fill the holes with epoxy, with a slight divet and then finish with gelcoat. Make sense?
Yes, assuming the holes are relatively small, say a ¼" or less. Also look at the pattern, is it one that might lead to weakening the structure, for example a series of closely spaced holes in a line.
 
Mar 23, 2015
259
Catalina 22 MK-II Dillon, CO
All small holes for screws to mount transducer, spaced at least 3/4" apart. OH .. thanks for the video links, Dave.
 
Aug 22, 2017
1,609
Hunter 26.5 West Palm Beach
I need to fill a couple of #10 screw holes from an old thru hull strainer for an engine intake (changing to a new pattern strainer).
If I understand you correctly, you are removing one flanged fitting & replacing it with another flanged fitting that has a different screw hole pattern. If that is the case, then I would just clean the old holes & fill them with 5200 before installing the new fitting. Since the new flange will cover the old holes, I see no need to epoxy/gelcoat, etc.
 
Jun 11, 2004
1,621
Oday 31 Redondo Beach
If I understand you correctly, you are removing one flanged fitting & replacing it with another flanged fitting that has a different screw hole pattern. If that is the case, then I would just clean the old holes & fill them with 5200 before installing the new fitting. Since the new flange will cover the old holes, I see no need to epoxy/gelcoat, etc.
Not a flanged fitting. Just a different strainer on the outside of the hull.
Thanks
https://www.groco.net/products/raw-water-strainers/hull-strainer/rsc-series
 
Aug 22, 2017
1,609
Hunter 26.5 West Palm Beach
I'm still thinking that a squirt of 5200 will do a good job in that application if the old holes are covered by the new fitting.
 
Oct 22, 2014
20,995
CAL 35 Cruiser #21 moored EVERETT WA
@JimInPB that should work with no problem. Be sure to clean the area so you get good adhesion to the fiberglass.