Thru hull spacer material

The plan is to install this male threaded thru hull onto a 90 deg. female elbow fitting so as to bring a hard line assembly up above the water line. My hull thickness (the sides of the hull) is 1/8". The securing nut only goes up so far onto the threads leaving a good 1/4" space left...I won't be able to tighten it up against the hull from the inside. I was considering using a hardwood or even aluminum for a spacer to act as sort of like a washer. Any ideas?
I hope this these pics help:

http://i1216.photobucket.com/albums...lbum to exhibit certain pictures/2e3725a2.jpg
http://i1216.photobucket.com/albums...lbum to exhibit certain pictures/193b08c6.jpg
http://i1216.photobucket.com/albums...lbum to exhibit certain pictures/32b62681.jpg

 

Good morning
Here in the UK we would go to a plumber's merchants and buy some thick neoprene or rubber washers.

 

Check standard garden hose washer for size. It looks like it may be close. You may need 2 to get it thick enough.

 

Rubber washers

The Maeleron fitting is bigger (diam.) than garden hose washers. Also, it has to absolutely water tight (over time as well.) I was thinking of something harder like a plate of aluminum or some sort of composite wood to in effect shim the hull make it artificially thicker than the 1/8" it is. Maybe IF I found the right diam. rubber washer that fit tight around the mushroom/fitting end without any gaps(leaks) I could stack those washers to take up the space. Can I use 5200 over rubber? Responses are appreciated. Rog

 

It doesn't need to be that tight on the mushroom fitting ,it seals on the flat surfaces.

 

Are you wanting some material to just seal the gap or something as a backing plate the strengthen the very thin 1/8th hull.

A hull strengthening backing plate of some sorts would be used by a professional builder on such an application like marine ply wood epoxied on.

 

You need to use a bedding compound rated for underwater use. Also, the threads don't go to the end because there is a backing plate required on the inside if the hull is so thin. Otherwise, it will end up leaking and the hull may fail too.

 

That's my question, what would you use as a backing plate: wood or composite plastic or aluminum? (my hull is 1/8" aluminum.) Is 5200 rated for underwater use?

 

Yes 5200 will do fine Aluminum would work. Make sure you put 5200 between the backing plate and the hull too.

 

Thru-hull spacer

Thanks, I was leaning towards going with the aluminum spacer as a back plate for that. I will take your advice with the 5200 between the spacer and hull too.