As to your question about vhf antennas,any 2 meter antenna,used by the ham radio band can be tuned for the vhf marine band.My personal choice would be a short mag mount antenna. Say less than 22 inches,as any longer you run the risk of having it hit tree limbs,which will detune it.As for using an ...

By saying high gain antennas,I assume you are referring to a mag mount type mobile antenna. The 3 element yagi is vastly superior to a high gain antenna since it is a directional antenna,and the high gain is omnidirectional,meaning all directions.