Replacing the Depth Transducer Thru Hull

 Replacing the Thru Hull for the Depth Transducer.

In February 2021, I replaced the old Airmar Depth, Speed, Temperature Transducer with the new NEMA 2000 DST 810, however I did not replace the Thru Hull as the boat was in the water.

Each time we return to the dock, I remove the DST 810 and replace it with a dummy plug. That dramatically reduces the amount of growth on the transducer - it actually stopped the 'S' part of the transducer working until I cleaned it off.

The reason for replacing the Thru Hull is simple! Water Water Everywhere and not what you want inside the boat. Pulling the Transducer out of it's Thru Hull would result in a massive ingress of water spewing up into the boat. I'm pretty good at getting the plug in as soon as the Transducer is removed, but it's still about a gallon of water and if I miss the spot, then it's a lot more.  The Thru Hull fitting that came with the new Transducer has a sprung valve inside that significantly diminishes the water ingress.

Step one - get the old Thru Hull out. The boat was on the hard for a bottom job so no water coming in :)

Getting the transducer out was not too difficult, I used my Vibro tool with the cutting attachment to cut into the plastic of the Thru Hull. 

The retaining ring nut didn't want to unscrew, did I see some 5200 in there?

I used a wrench to break off bits of the Thru Hull, had to be careful not to damage that hose, it's a bilge pump hose.

Making progress. I can see daylight.

Probably spent about 10 minutes getting this far.

Finally got it out.

peeled off the old sealant and sanded it down ( after this pic ) then cleaned the inside area.

I sanded the outside too and formed a countersink on the underside of the hole to ensure the new sealant formed a water tight seal.

Peggy was with me, so after cleaning the area with Acetone and applying 4200 to the outer flange of the new Thru Hull and on the area around the Thru Hull on the inside of the hull, Peggy held the fitting up from the outside and I slipped the rubber ring around the threaded portion of the Thru Hull protruding inside the hull. Then on went the retaining ring nut. As planned, 4200 squeezed out of the edges of the ring and, outside, the flange of the Thru Hull. That's not going to leak!

Before tightening it all down, we made sure the Arrow on the outside of the Thru Hull was still pointing forwards - not sure why - but it was perfect. Good Job Peggy.

New Thru Hull installed.

Yes, I know, it's crowded down there. 

The blanking plug can be seen laying on it's side at the bottom of the picture.

It has a yellow O-Ring, so does the Transducer but you cannot see it when installed into the Thru Hull.

The previous Thru Hull required black O-rings, slightly different in size.

Plan is to splash the boat on Tuesday 12/19 - I'll know if it seals correctly then 😉

Of course, I'll inspect it before they remove the Boat Lift Slings.  Check out my post about replacing the Packless Shaft Seal - I'll be checking that too!

See you on the water.