Running them dry will certainly destroy them.
I planned to replace the one on my 30 hp Tohatsu when I had to pull the
lower unit for another reason, and I found one blade (lobe?) nearly broken
off. I think MAYBE I had at some point run it dry for just a couple of
seconds, so maybe that's all it took.
IIRC, the parts man where I got these parts said Tohatsu--or maybe all
Japanese ob's -- had rather weak impellers.
Like I learned after having to replace bearings on boat trailer wheels
....keep the axle OUT of the water!! In this case... keep the lower unit IN
the water!! When it's running,of course.

"Walt" wrote in message ...
I have a less than one year old Tohatsu 4stroke 4 hp motor that I use on
a canoe. Ive treated the engine well except one time when the motor was
transported with the propeller end too high and oil leaked into the
head. The motor would not start until the head oil had leaked out and
when the engine finally turned over, it started and ran for about maybe
30 seconds (out of water).

I took the boat out this weekend and there was no cooling water flow. I
took it to the shop where I bought it new about 9 months ago and was
informed that I have a bill just under $300 to fix the water pump (and
to change the bottom end oil).

Is this common with all brands? Are these water pumps very fragile. I
read the Tohatsu warentee and it says water pumps are not convered (or
something like that, I wonder why they dont warrentee the water pumps)..

Im not real happy with this problem but have really enjoyed the boat.
Its a 15 foot square stern canoe and the 4 hp 4 stroke moves it along at
about 8 mph with the motor and it really takes an effort to burn more
than 1/2 gallon gas all day. The canoe is really nice to row - heres a
picture of the motor with a "goofball - but works really well" mirror
attached so that you can see where you are going when rowing

http://analogengineering.com/elevenm...ew_mirror1.jpg

This lake is in Colorado.

wh