Thru- hulls and transducers

[Chuck Scheaffer]

Sharing my story in the interest of helping.

When I upgraded my instruments, I had to cut larger holes into the hull for the new larger diameter sensor thru-hulls.  The trick to cutting a larger hole where you already have a small hole is to make the pilot plug the same size as the existing hole.  In other words, find a hole saw that matches the existing hole and cut a plug out of 2 x 4 and slip that plug onto the pilot bit of the larger hole saw so it keeps it centered.and drill the larger hole.  I used flush thru-hulls and used different size hole saws to chamfer the fiberglass which is about 3/4" thick here.  The discolored outer hull shows the layers of barrier coat and fairing compound.

Chuck Scheaffer

I attached more pictures..