Gotta jump in on this.....supporting info. Years ago, back in the '50-'60's era, Mercury had a test site at Lake X in Florida where they beat their engines to death. Power trim was pretty much non existent at the time. Engines were just hung on the transom and gravity kept them vertical.
Running their test boats over logs and sand bars and such, at high throttle settings, if an obstruction was hit, knocking the prop out of the water, there was no limit to the engine rpms encountered and when gravity took over and the prop came back down, spinning at several thousand RPM, making water contact, you had this tremendous "slam" against the transom the could break the engine mounting structure or knock out the transom.
So, taking the 40 hp Mark 55 as an example, maybe '56 for a year model, they installed shock absorbers to prevent the slamming and somewhere along the way decided to use a level sensing Mercury (chemical element, not engine brand) switch to kill the engine so that when an obstruction was encountered the prop wouldn't be spinning at several thousand rpm.
Mercury switches are usually in a sealed container with inert gas and there is no corrosion, nothing to spark and last indefinitely. I'd look elsewhere.
Back to the shocks: When Merc did come out with Power Trim, like I had on my mid '70's Merc. 850, the shock absorber mounting pattern made a perfect place to install power trim....just add operator controlled powered hydraulic fluid to the shocks and wala....instant Power Tilt and Trim.
