Thru-Hull Replacement - another story/experience

[Pete1313]

So, I there are a ton of posts on this subject here, which have all really helped me out...however, I encountered a problem today in replacing two of my thru-hulls that I hadn't seen a post about....so i wanted to post my experience and see also, if anyone has the same.....

Today I replaced the aft bilge and starbord fishbox drain thru hull. The original plastic ones literally disintegrated in my hands when my new/used 1997 Voyager 248 arrived here from CA....

On both of these thru hulls, I found that the thickness of the hull/glass was greater on the lower half of the thru-hull hole than the top half. This resulted in me having great difficulty tightening the new stainless/bronze thru-hull fittings. What would happen is the bottom (thicker) part would cinch first, and cause the top (thinner) part to separate-- with the end result being a thru-hull where the outside flange was not flush with the outside of the hull all around. With the stainless one I installed (came with a nylon washer) the washer squished up to the top side.

We ended up solving the problem by crafting some shims to fit between the top half of the thru-hull nut and the hull, allowing equal pressure to be exerted on the hull, thereby pulling the thru-hull fitting in evenly and flush.

Has anyone else experienced this? How did you deal with it?

I will be replacing the remaining thru-hulls next winter (doing just enough this season to get me on the water by May 1).....any info is appreciated!

Thanks, and tight lines.....

 

[JeffN]

Not much of an engineer here but I think your fix sounds pretty good. Did you glass in the shims before installing the thru hull? Would you even need to? I would guess your fittings are above the waterline right? I'll be interested to hear other opinions. I replaced a fish box drain thru hull and the drain hose on my '83 last year. The fitting is at the water line so it is always partially below the water line at rest. I had a similar problem to yours, hull thicker on the bottom than on the top of the fitting because on mine it is just above the chine area. When I removed the factory fitting I found that because of the uneven thickness the fitting had been cross threaded when installed. This exerted uneven pressure on the "stem" of the fitting. After I removed it I found that the fitting was cracked at the outside end of the stem about three quarters of the way around the fitting. This fitting was nylon, I think, an accident waiting to happen. Granted it did last twenty six years. I should have replaced it sooner. The new fitting is bronze and it snugged up nicely when installed. I used 5200 to seal it. This season I am tackling the fuel fill hose and vent among other things.

 

[Workdog]

I installed an Airmar B60-20 transducer which is also a thruhull. The inside surface in the bilge where I wanted to install it was uneven also, causing the outer flange to seat unevenly when I dry fitted it. I used a dremel with a sanding bit to level the high edge of the inside hole.

 

[richie rich]

sounds like at or near the chine GW had some extra glass..probably from the initial tabbing and overlap which is common.......if you shimmed it and used 5200 its probably not going anywhere for a long time....but if you have some access to the area, I would rough up the area a little and epoxy in a little glass or even just thickened epoxy with milled fibers to even out the spot....this would make it flat and permanent....then just install your fitting as normal.

If you have a thick area like what Workdog had, then sanding down (a little) will be fine....but the gunwale area is usually thin to begin with...I'd rather build it up than sand it down.

 

[Pete1313]

Well, the aft bilge pump thru-hull was above the waterline about 18"...but where it was located, the glass structure below started to thicken as it is in the transom area. (Very impressed with the amount of glass and reinforcement in my transom-- including the steel plate!!!)

We ground it down a bit and put some epoxy over the exposed glass. The shim is not glassed in. I used a ton of 4200 (just in case it ever has to come out). I do not think water will be coming through that.

The fishbox drain is down on the starboard side, at the water line, and it too had an issue. again, didn't glass the shim in. In fact, that one was so hard to get to, we were lucky to get the shim in behind the nut. However, it cinched down flush, gooped it up with a ton of 4200.....its not going anywhere and is tight as a button.

Ideally, we'd have built up the low side with glass, but due to access issues, that was not possible.