One more thing......I'd prefer them to be nylon rather than stainless steel.

if you are asking this question re a kayak rudder, you can make the through hulls with nylon tube (similar to a bicycle cable for breaks).  you can build up the exit on the hull with some extra wood around the exit to shape it anyway you want.

as for water tight, you can run the  tube from the through hull in the back of the boat all the way to the rear bulkhead so no water would enter your enclosed rear compartment.  is it 100% water proof? depends how you define it...but based on what i am suggesting it keeps the rear compartment waterproof.  

the tighter the tube to cable relationship and the more it is above the waterline, you can end up with no real exposure to flooding.

h

Agree with hspira's post above.

On two boats, I just ran the tube through the deck and cut it off at an angle.  Not supoer pretty but not too bad.  This in the Wahoo.

On my later builds, I started using these fittings from Stellar USA.  The tubing glues inside the fitting under the deck so everything is water tight.  The fittings work well on this decks but may require some trimming if the deck is thicker.  

You did not say what type rudder system you are using, but you may want to consider using 2.3mm Dyneema line that is used in surfskis instead of cable.  It is expensive but much easier to adjust.    

Thanks Mark, that looks like the type of fitting I need.    I'll send the pic off to a few marine supplies places and see what I can come up with.

Thanks also hspira.   I had considered what you're suggesting, and may yet do that if I can't find Mark's fittings locally.

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