Hi Brad, there's some good information on this message board using the "search" feature.

From the handful of Expresses I have inspected, there is a dedicated location for thru hulls. It is built up solid fiberglass and raised a bit (about 5" by 5"). Mine (#100) is located beneath the most forward part of the floor board which is OK since my Signet speedo unit is shallow and does not protrude (though it was necessary to cut a hole in the floorboard).

An earlier express hull number had their dedicated location (solid core, no foam) just forward of the floor board underneath the first V-berth hole. Mine has a battery tray platform in that place.

Another Express has theirs mounted well forward of the of that V-berth hole and keel, and it appeared that it was a dedicated location since it was built up solid core.

My considerations for mounting a thru hull were: 1. Could I accidentally damage it by stepping on it or heavy gear slamming into it. 2. How flush was the unit on the waterside of the hull. 3. Self-installation. 4. Easy inspection for any damage that could lead to water intrusion. 5. One hole only in the entire hull.

When I wanted to replace my signet knotmeter with a triducer, I considered the Raymarine DST800, but I did not want to increase the diameter of my existing hole or have it protruding out of floor board or hull where I normally step. Plus, the DST800 did not have a flush mount option and because of the radius of the hull, the mushroom would not be flush against the hull. If installed professionally, they can recess and flush mount them well.

Eventually, I kept the Signet unit since they still make them and just added a inexpensive Norcross, inhull epoxied depthsounder. I mounted it in the dedicated location right next to the thru hull signet since the Norcross unit is fairly small. I was unable to find another location on my boat that the Norcross would shoot through.

I will try to add a picture to the files.

JB

:: Looking for advice on the best location to place the
:: thru hull fitting for a knot meter. Thanks