Welding Stainless Through-Hulls to a Steel Hull

[AJS]

Marelon valves on plastic through-hulls is a good solution. I had these in a steel cruising yacht for >13 years and had no problems at all. If they are to be fitted in the engine room, consider the consequences of fire. If you do opt for welded s/s nipples, ensure that you use the correct electrode. 308s or 309s i believe are still the recommended rod for welding s/s to carbon steel. But check with a good welding consumables supplier.
I dont see enough advantage if any for using s/s.