Location of thru-hull for speedo

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Postby Guest » Sat Jun 08, 2002 5:32 pm

I would like to mount a speedo and got location info from TPI for the solid glass area intended for speedos. But upon drilling a small hole from the inside to make sure I wasn't hitting wood I did indeed hit wood.

Does anyone know where TPI placed the solid glass area for speedos? For they don't seem to know where it is.

I would rather not cut, rout, and fill etc. a hole through the balsa core. TPI claims there is a 4'x4' solid glass area 20 inches forward of the bilge sump and 12 inches to starboard of the centerline. (Right next to battery - smart!)

Postby Guest » Sat Jun 08, 2002 6:35 pm


That's exactly where I found the solid area on my boat, just forward of the battery mount, starboard side. On mine you could actually see a slight depression of the inner skin that delineated the area.

Postby Guest » Sat Jun 08, 2002 8:26 pm


Was your spot the distances I mention? I can't look at the boat now, but I'll check for the depression. I guess I could make another exploratory hole and maybe I'll strike oil.

The spot I measured to was forward of the battery mount and at the outboard edge of the battery mount. Is yours more inboard?

Thanks for the response.

Postby Guest » Mon Jun 10, 2002 12:03 pm

I'm not sure if they have changed the locations over time. My boat is #32. It has two solid core locations. One is center line, forward of the mast under the air tight liner. It is easy to spot because the inside of the hull is not painted and you can see thru the glass. My speedo is located there. Another spot is on starboard about 8 inches from the centerline in line with the mast. I'm not sure where your battery is mounted, mine is under the starboard settee. This may have changed over time.

May I suggest sanding the paint off rather than drilling exploritory holes. If you use a 120 grit to get the paint off, then 400 fine grit wet sand to polish, you should be able to see if the location has balsa or not.

Good luck.

Postby Guest » Wed Jun 12, 2002 7:12 pm

On mine #340, the solid area was clearly visible on the inside, a 4"x4" square. Unfortunately, mine was more than 16" off-center, too far off centerline to use anyway. So I drilled close to center both sides (speed & depth), dug out the core and filled with epoxy (you MUST do this) to get a solid area. Works fine in case your solid area doesn't pan out.

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