thru hull fittings

[Destroyer]

Originally Posted by SkunkBoat

never use BRASS in ANY fitting that makes contact with seawater, ever. It contains copper and zinc and zinc "disappears" in salt water, weakening the brass.
Also, never use a Brass fitting on aluminum (such as fuel tank) because of bi-metallic corrosion.

Bronze contains copper and nickel and does not have the same problem, provided that you bond them in common with all other submerged metal( the motor and all other fittings). SS also needs to be bonded.

A big PRO for using MARELON is not needing to maintain a good electrical bond

Skunk, gotta slightly disagree with you. While what you say is true as to the make up of normal Brass, I've personally had DR Brass fittings in a boat for long years with no signs of degradation. The so-called dezincification resistant (DZR or DR) Brasses, (sometimes referred to as CR (corrosion resistant) brasses), are used where there is a large corrosion risk and where normal brasses do not meet the standards.

Additionally, part of the reason I've never had any problems might be that all my boats are trailer queens, so the bottom is never in salt water for long periods of time and is washed down with sweet water as soon as it gets back home.

Bronze is principally an alloy of copper and tin. But Bronze does not necessarily contain tin, and a variety of alloys of copper, including alloys with arsenic, phosphorus, aluminium, manganese, and silicon, are all commonly termed "bronze"

Wholeheartedly agree with you on dissimilar metals causing electrolysis, which is why it's so important to not neglect the sacrificial Zinks on your engine.

And I'll stand by my original comment that my own personal choice for thru-hull fittings is SS, which suffers from none of the aforementioned possible problems.

(I know that Marlon is a superior grade, glass reinforced plastic, and it's probably a great choice for just about everybody, but given my druthers, I still like SS better. I've never stripped the threads on a SS fitting like you can with plastic, so humor an old sea dog)