by Ianfs » 07 Dec 2014, 23:14
There are many manufactures, but the top ones tend to be Quicksliver (Mercuisers own), Sierra or Technoseal. GLM I'm not sure about although they seem to be in the top suppliers in the US.
A lot of manufacturers tend to swing towards Aluminium for Sea Water rather than Zinc.
My opinion, I've tried Aluminium and am not sure it is entirely genuine for Salt i.e. the Aluminium would have to be a lower grade that that of your Sterndrive and that's debatable. Therefore I would say that as long as you use a Zinc Kit made kit and then sold by a reputable company like the ones mentioned then you should get along OK.