Well I have been wait for warmer weather to start mounting my humminbirds 997c SI Combo and 957c but not before receiving my mounts first. After dishing out good money for these units, I did not want to just mount them. I bought some Ram Mounts to protect my units from any vibration and shock that they will be subjected to during the upcoming season. With the size of these units and weight of them you need a product that was designed to protect them. Having used their products in the past, I know that they work extremely well. Before adding these mounts to my boat after I decide where I want them to go on my boat I will purchase some stainless steel bolts, washers, lock washers and nuts. The stainless steel will not rust out over the years and will protect my units from breaking off at the base of mounts due to the bolts rusting out. I will also add some lock tight to the threads of the bolts to ensure that the nuts do not loosen off aswhile. Even if I do find some stainless steel nylon washers, I will still add a drop of lock tight to the threads just for peace of mind.
I hope this is helpful to some of you that are looking at an option to mount your units to your boat with peace of mind of knowing that they will be safe from damage for the upcoming season.