Yep, I'll second Bumble's comments. (Have used Suz controls on a Yam, Mariner control on a Johnson......)
Only possible problem you may have is the wiring for the E-stop and / or starter. There's a chance the loom from the remotes will have a different plug to the one on the engine. But if your new Mariner is old enough it was probably made by Yamaha anyway!
If your old 55 is totally dead and happens to have a working PTT can I make you an offer for it?