I used to use WD40 or CRC 656 for years on my old Johnson. About once a month I would take off the cowling and spray the engine down, wires and all, to protect from corrosion. After a couple of years, the spark plug wires and rubber boots would get brittle and crack. I read on a boating forum to use a silicon spray instead, that it would not harm the rubber on your engine. I have been using CRC Silicon spray on my current Johnson for the last three years, and the engine is spotless, with no rubber cracking. I don't know if some of you guys already do this, but if not, give it a try. -Joe