If positive displacement pumps dont self prime at start up, they need
repair. Sometimes the cover plates are grooved and worn allowing air in and
the pump will not create a suction. Replacing expensive impellors without
fixing the end plates just allows them to overheat and crack. Buy new
plates or repair the old ones. They have to be smooth and flat. You can
repair a plate by turning it over, filling with epoxy etc... or gluing on a
flat metal plate.

"John" wrote in message
om...
"Tony Abbott" wrote in message
. rr.com...
On the installation of a fresh pair of marine engines how do you prime
the
raw water pumps. Each engine has a Sherwood (G7 I believe) with 1 1/4"
inlet/outlet. The boat is currently out of the water as we are
finishing a
long restoration process. I have a garden hose with the water intake
adapter hooked to the intake under the boat (yes the correction piece
for
raw water pickup). The path the water goes is intake from under the
boat,
through a raw water filter, through a transmission oil cooler then to
the
pump. There is about 5' worth of hose and the filter and cooler prior to
reaching the pump.

Thanks in advance for the priming answers/suggestions...

Tony, your raw water pumps are self priming, their is no need to prime
them. But someone showed me a trick years ago, pull the hose off
between the pump and the engine (or heat exchanger) squirt some liquid
dish washing detergent down into the pump, replace the hose. This will
provide lubrication to the pump while it is running dry, drawing water
up into it. It will also let you know if the cooling water is flowing,
just look at the outlet, you should start to see bubbles.