Under water thru-hull

[Dirty_Oar]

So I have a 1999 Seaswirl Striper and the factory deck scupper Thru-hull fitting is worn and degraded. I was looking at replacing it and upgrading to stainless thru-hulls with the built in flapper. Problem is I was doing some research and it seems that Stainless isn't recommended for below the waterline. What are you guys running/recommend for a below the waterline thru-hull?

 

[casper5280]

They only come in bronze and Fibre Reinforced Plastic quite tough however I would use one. Bronze fittings rather than plastic or Stainless Steel if I was replacing thru-hull fittings. FRP is fine for log fittings where there is little or no stress on the fitting but I would not trust FRP fittings in any underwater application on the boat. One hit from a decent piece of wood and your going down! Quickly! The other thing to remember is your shut off on the other side of the thru hull has to match, you don't want any corrosion starting because of dissimilar metals. Another thing to do is have a plastic or wooden plug to fill that hole if something was to ever happen to that fitting.

 

[SteelyDan]

Go with bronze

 

[profisher]

I replaced the plastic outer housings on my Seasport to stainless which I had custom made by Crest Sheet Metal. The plastic ones were just starting to show fine cracks around the holes for the mounting screws. Stainless is a big upgrade over the original ones. At least now if a log bumps into one of them it won't break off. Mine are the ball type not the flapper.

 

[casper5280]

Sorry didn't read post properly, did not see that they were deck scupper though hulls. That said I would still go to a metal though hull.

 

[ryanb]

I replaced a bronze thru hull with an expensive Marelon FRP one. The body broke in half while installing it, I guess from too much torque on the backing nut. Didn't leave me with a high degree of confidence in the durability of these plastic thru hulls.

 

[searun]

For commercial operators we must use metal thru hulls with shut offs. Cannot use plastic. There have been quite a few sinking vessels due to plastic which degrades over time and fractures. Below waterline I use bronze. Above for cosmetic reasons, stainless. If you are replacing a below water thru hull best to use a proper flange and backing plate that you glass into place.

https://marinehowto.com/replacing-thru-hulls-and-seacocks/

 

[ab1752]

Hey Searun thanks very much for posting that link as it was a great reaad. Our Hourston, particularly the throughull for the bait well, is simply threaded through the hull and does not have a bolt though flange. I never use it and it is in a tight area but by chance I noticed last fall that the ball valve screwed onto the through hull was in very bad shape and clearly leaking. I changed it out with a marine grade ball valve and will watch it but for sure, this keeps me up at night. I can't easily access the other through hulls in our boat that I am aware of but I will be all over this. The deck self bails too and I will for sure be checking those this weekend.