Ron Thornton wrote:
Nothing, thats why you do not run them more tha 30 seconds without water
coming out.

And why impellers require replacement at least every couple of years as
part of preventive maintenance...'cuz even a couple of seconds of dry
friction heat each time wears the edges of the vanes a little...it's not
something you can see just by looking, and there's only a microscopic
amount of difference between vanes that fit the housing tightly enough
to pump water and vanes that don't. Replacing 'em on a schedule
definitely beats being forced to do it when the pump quits...keep the
old one as an emergency spare--'cuz sand or debris can destroy even a
brand new one...applying some teflon grease when you install it helps it
last longer.

--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and
Other Sources of Aggravation and Odor"
http://shop.sailboatowners.com/detai...=400&group=327

http://www.seaworthy.com/html/get_ri...oat_odors.html