Sorry I don't have the reference, but 3 years or so is the "recommended"
impeller replacement schedule. And that I think is based on a 100 hours or
so season. I also understand that the newer impellers are built to last
longer. My approach ... pull the outdrive every 3 seasons to lube the
u-joints etc, and while it's off replace the impeller. And then there are
people run their boats 10 years with no preventive maintenance and have no
problems :-)

"Mark" wrote in message
sgroups.com...
I have a 350 with an Alpha 1 that is overheating at low rpms. Diagnosing
the same problem last year, I had to have the water pump in the lower unit
replaced. I will troubleshoot all other possibilities this weekend
before
having to pull the boat out, but thought you folks in the news groups may
have some ideas as to what other causes it could be.

The boat is an 86 and I have owned it for about ten years for having to
replace the outdrive water pump. Any estimates as to what the life
expectancy of the water pump should be?

First I will be checking for leaks, then changing the t'stat on the engine
(as I do not recall when I last replaced it), but beyond that, Ican only
suspect either the new (last year) pump has failed prematurely, or the
mechanic I hired to do it did.

Mark (the rail & canopy hook guy)
www.ripnet.com/vtf/prod03.htm