Humminbird ducer arm

Anyone know what size bolt I need to connect a Marcum arm to a Humminbird ice55? Just ordered the arm but it came without hardware.

I believe it is a 1/4 20 bolt.

I suggest you take the arm and shuttle to yrou hardware store to figure out what is needed. I did this to 3 of my ICE 55’s but would not even start to guess what size hardware is needed. I remember adding several washers as shims and so forth.

It should take a 1/4-20 screw, like FT said. I also stacked washers to make mine work right on my old 55, like dunker said.

Wormdunker has the best advice here.

Head up into a smaller, quieter hardware store (ACE Hardware) and have at it! I’d brought armfuls of stuff in there to figure out what’s right. Just tell the clerk what the plan is.