Welcome RJM to the community.
I am not sure about the validity of the zinc affecting the fuel injectors. I am sure there is some form of validity, but I am not aware of it. I think the issue with using Galvanized piping in fuel systems is the introduction of foreign particle contamination into a system that is suppose to operates in the cleanest possible environment. Galvanization, hot dip or the likes are a coating, and it will fail at some point in time. Those small particles will cause problems to your injection system and its machined tight tolerances.
Standard black iron piping is recommended for fuel applications. Finding galvanized piping is not the end of the world, requiring pulling out, but it does raise eyebrows on possible shortcomings in your overall operation - the building or modifying of the vessel's systems. I would however, make sure that the piping post filters, is replaced with proper piping. This will eliminate possible contamination after your filters.
This exercise would also be a good time to evaluate your filtration system; primary filters should be able to handle these impurities, but I would make double sure what your filtration is and modify accordingly to required specs. Generally racors - or the likes - offer 10-30 microns filtration, with your secondary down to 2-5 microns. Check your engine manual for fuel quality and filtration specs (micron size required) to make sure you are able to meet these specs.
Hope that helps.
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