I just learned a thing or two about grease and thought I'd pass it on.

I like putting grease on stuff. It keeps electrical connections protected and keeps seawater from corroding a lot of stuff.

I recently greased a new set of boots (drive and exhaust) and put them on the drive. Another problem popped up and I had to pull the drive about a month later. I was surprised to find the nice coat of grease I put on the aluminum mounting surface that the boots were clamped onto, had reacted with the aluminum and just turned into crud.

This made me think of how impressed I was when I removed the raw water pump after 10 or so years and found my o rings still fresh with the grease I had put on them when I last serviced it. The difference was the grease that I used. Both were in contact with aluminum and seawater.

The grease I used on the outdrive was a marine grease for wheel bearings and is apparently good for seawater and steel situations. But that same grease had reacted with the aluminum of my outdrive.

The grease I used to dress the o rings on my raw water pump was a "silicone compound" and was not called a grease at all. It was the Dow Corning 111 that I had gotten my hands on some time ago. It is water resistant and more important to me, does not react with metals even in the presence of seawater and is also inert with the rubber o rings used in our cooling systems, where petroleum based greases will cause the rubber o rings to swell.

I don't like the tenacity of the "silicone compound" when it comes to removing it from surfaces like hands, steering wheels and rags. Its just a pain in the butt, but it works like a son of a gun when you want it to stay put!

The Dow Corning 111 is pricy but I found a "direct comparison" material on the net that I can not tell the difference from the DC 111. It is "Jet-Lube Silicone Compound DM" and I am quite happy with it. I have used it in my outdrive water tube steering bearing and all other aluminum surfaces as well as o rings and have full confidence in it. I will not be using wheel bearing or any other petroleum based grease on aluminum or rubber surfaces again.

Just thought I would share this with folks. I hope this is useful and saves someone a painful or expensive learning experience.