View Full Version : Make hole in hull bigger

04-30-2012, 10:58 PM
Any pointers on this before I plug in the drill? I don't want to chip or crack anything.


I need to bore out the hole the speaker wires are in. I need it big enough for some sort of rubber sleeve for the wires.

05-01-2012, 01:53 AM
How much bigger do you need/want to go? You may be able to get away with just a shrink wrap type tubing cover over the wires instead of a loom or bulky sleeve and then not have to open it up that much at all.

Normally you tape over it really good and if using a hole saw, some run it backwards to cut through the gelcoat, then flip the switch and finish off the hole. But since you've already got the hole I'm wondering if you could get away with using a step drill bit. Just not sure how gentle that would be on the gelcoat, even with tape on it... :shock:

05-01-2012, 08:24 AM
Perhaps one of these would work?


If not then that looks like it is about a 3/8 hole already. But to be sure what size is the existing hole? You can pickup many size drill bits at Lowes or Home Depot. So if the existing hole si say 3/8 and you want to nudge it up a touch buy a 1/2 bit and run it in reverse to enlarge the existing hole. I'd then hit it gently with a step (conical) bit in reverse to taper the gelcoat a bit.

05-01-2012, 09:04 AM
looks like theres enough room to squeeze some wire loom in that. I'd run loom and leave it if it was mine.

but to the original question, I'd probably use a dremel very slowly with tape across the whole area and a green metal stone bit on it.

05-01-2012, 09:42 AM
Indeed if you just wanted the wires cleaned up some I like this braided sleeving and secure the ends with heat shrink tubing.


05-01-2012, 05:38 PM
My advise is if you only need it slightly bigger use a file, or get the small bits with the sandpaper on them. The same as you would see on a Drimmel. If you need it larger then you can use a larger drill bit, run it in reverse. I would not run it forward at all with a pre drilled hole that size, it will grab and gripe and try to chunk out the gell.

05-01-2012, 05:45 PM
get a round file with fine teeth and mount on the drill and slowly work the hole til it is open enough.

05-01-2012, 05:49 PM
I would not run it forward at all with a pre drilled hole that size, it will grab and gripe and try to chunk out the gell.

That was my worry. I think I'm going with KSmiths idea, with a twist.
1. Start with what he suggested. I think we've got some of this stuff with our videoconference group. About a foot and a half. I've got some heat shrink at home.

2. I've already got some ribbed plastic wrap. I'll use this as a "water proof" cover.

3. I'll ream out the hole with an air grinder, big enough to fit the ribbed plastic wrap into the hole and silicone closed. Might get a little dusty, but no gouges/chips on the surface.

Thanks for all the input.

beat taco
08-03-2012, 01:28 AM
Not that you need to go with a hole saw but if you ever do and you have a pre existing hole use a piece of 3/4" plywood with the new hole drilled in it. Simply hold the plywood over the old hole and drill the new one. I was able to drill all five of my courtesy lights larger with no help since I could rest the plywood on my floor. To drill my five vent holes bigger I held the plywood and had a friend drill. All holes need to be filed after drilling or cracks will appear in your gel coat.

08-03-2012, 10:46 AM
stick an appropriate sized cork in the hole for the hole saw center bit to bite on. I did this when inlarging my drain ports to 1". Worked like a charm.

08-03-2012, 11:12 AM
I posted this hint given to me by 11 Outback V.

Get a hole saw kit that has the spindle & interchangeable hole sizes. Stack the current hole size inside the desired hole size and the smaller bit will act as a guide/hold it in place.

08-03-2012, 12:25 PM
Easiest and safest method is to use a round file. It'll open it up in less than a minute and not risk destroying the gel coat. Put the power tools down for this job. When I put new thru hulls in I had to go a little lager than the 1" hole saw I used to make the initial hole. I used a round file and I swear it only took a few swipes to make a significant different to the size f the hole..