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Author Topic:   How do you properly mount screws on deck? How do you fill old holes?
ShrimpBurrito posted 06-26-2002 02:21 PM ET (US)   Profile for ShrimpBurrito   Send Email to ShrimpBurrito  
1) How do you properly mount screws on deck?

First, pre-drill and countersink if necessary. Inject (with syringe?) some kind of epoxy in hole as a sealant/screw adhesive. Insert and tighten screw. Should I use silicone instead of epoxy?

2) How do you fill old holes?

Inject epoxy into hole, leaving ~1/8" at the top. Fill that 1/8" space with gelcoat and sand to make flush.

Am I doing this right? Any suggestions?

Jimm posted 06-26-2002 06:13 PM ET (US)     Profile for Jimm    
I'd be interested in the answer also. Up ya go.
JohnAz posted 06-27-2002 12:13 AM ET (US)     Profile for JohnAz  Send Email to JohnAz     
I drill a hole epoxy a wood dowel in the hole, drill the dowel, and screw the screw in
Tom W Clark posted 06-27-2002 10:50 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

Could you be a bit more specific? Are you asking how to screw into the hull where there is no wood backing?

The general answer to your question is pre-drill and countersink if you want to minimize gel coat chipping and to seal the screw hole with a sealant.

Your choice of sealant is not super important for just a screw. Any of the polyurethane caulks will work even the super tenacious adhesive caulk, 3M 5200. A Polysulfide caulk like 3M 101 or Boat Life LIFE Caulk are good too. Silicone will work as well as will Polyseamseal Adhesive Caulk (a latex).

You generally don’t want to epoxy a screw in place unless there is some special reason like it’s a stripped but not a really stressed fastener so a little epoxy will suffice.

Filling old holes has been covered dozens of times in the FORUM over the last two years, but here is the short answer:

Make sure the hole is dry and clean. Drill it a tad larger if this will clean it up. If the hole is large and deep enough, then pre-fill it with something. Whether you use caulk, epoxy, foam or what have you will depend on the nature and size of the hole.

Small screw holes can simply be filled with gel coat patch paste.

Make sure this pre-fill is not up to the surface of the gel coat, or if it is then route or drill it down about 1/16” and fill with gel coat patch paste in the color to match.

Once the gel coat starts to kick, then scrape it down almost level with the surrounding hull and let it finish catalyzing. Then sand and buff it out. Done correctly, screw holes can be made invisible.

ShrimpBurrito posted 06-27-2002 12:28 PM ET (US)     Profile for ShrimpBurrito  Send Email to ShrimpBurrito     
JohnAz - Thanks for the reply. Nice idea.

Tom - My apologies for not searching for the answer before asking. I should have known something like that would have been already covered.

In any event, I was not aware that you could effectively mount anything on deck where wood is not behind it. Is that not that case?

Tom W Clark posted 06-27-2002 12:38 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

There's not really a yes or no answer to that question. Lots of things can and are mounted to the fiberglass skin only. If there is not much strain on whatever is being attached it's OK. Pad eyes, fuel filters, lights, transducers, microphone clips all get mounted to non-wood backed areas. It's not the not of the world. Of course the mounting will be stronger if there is wood back there but it's not always possible to choose a location with wood.

Regarding the use of a dowel as screw backing, this is not such a great idea. A wood plug is much better. If you use dowel, you will be driving the screw into end grain which will have only a fraction of the withdrawal strength of wood where the grain is at 90° to the fastener. This is a very common mistake and one to be avoided.

ShrimpBurrito posted 06-27-2002 01:22 PM ET (US)     Profile for ShrimpBurrito  Send Email to ShrimpBurrito     
Thanks for the advice, Tom, especially the clarification on dowels and wood plugs. I thought they were the same animal.
HAB posted 06-27-2002 02:03 PM ET (US)     Profile for HAB  Send Email to HAB     
Thank you for the clarification on the dowel vs. wood plug. I never thought about the strength issue, but it makes perfect sense.
I am about to mount the chocks for my new cooler and I have to fill some holes.
I am also relocating my RPS a few inches to the stern and I filled some caverous old mounting holes from the old location with 5200. Not all were bone dry. I did drill them oversize, but stopped at about 1/2 an inch. Do you forsee any problems?
JohnAz posted 06-27-2002 02:21 PM ET (US)     Profile for JohnAz  Send Email to JohnAz     
dowels or plugs, i have even put a 6 in x 4 in x 4 in oak block under the floor of my 13ft-er, to mount a console to,,if properly covered with marine tex, or original flooring the plugs are totaly invisible
Tom W Clark posted 06-27-2002 03:08 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

A hole that will be covered can easily be filled with 5200 or one of the other poly caulks. The moisture will only help it cure. You will be fine.

John O posted 06-28-2002 12:44 AM ET (US)     Profile for John O    
Now I am confused. Regarding mounting things to the deck. If I want to mount to an'88 newport; and am not sure if there is wood behind the gel coat or if I beleve the wood is would I mount say ....cooler chocks if a Woodchuck could chuck wood.. ok I am getting off track.

what are the rules for mounting stuff to the deck? I have gone back and seen the wood diagrams.... I keep hearing about the negs, of drilling holes in a whaler. does 3m 5200 really prefer to set up w/ dampness?

Tom W Clark posted 06-30-2002 04:14 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
John O,

Well, if there's wood backing then you've got no problem. If there's not then it depends on what you're trying to attach.

Cooler chocks should find plywood backing just about anywhere unless you have an old 16' hull. If your boat is a 1988 Newport then you’ve got plywood backing and you just screw the cooler cleats to the floor being sure to seal the screw hole with some caulk so water can't get in.

There's nothing wrong with drilling holes in your Whaler. Just seal them so water can't get in.

Yes, polyurethane and polysulfide caulks cure by contact with moisture, they do not simply “dry”. It’s one of their nice qualities for use on boats.

jking posted 07-06-2002 11:16 PM ET (US)     Profile for jking  Send Email to jking     
While reading about filling screw holes in figreglass I thought of a question no seems to know a answer. In my splash well the owner before me had a oil tank for his outboard mounted with screws. I took the tank out and repaired the screw holes with gel coat and it looked great. Later the patched screw holes started seeping some oil. Before I patched the screw holes I cleaned the holes good but I guess there is still some oil left inside. Any ideas how to get the oil out?

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