Yes, my Gilkes pumps are centrifugal, non positive displacememt pumps where the bronze impellers do not touch the pump body, much like a swimming pool circulation pump.
The pumps are 30 years old, 27 years in active service, of which I have had control for 15 years.
At rest, the pump sits half full of raw water as indicated by the corrosion line in the pump chamber. The impellers displayed uniform corrosion, but suffered from erosion at their perimeters.
What caused me to open them up was the ceramic raw water shaft seals started to leak about a drop a day about 2 years ago.
A couple of notes on use of this kind of pump.
- They will not self prime, so you have to fill the raw water circuit should you drain the system. I drain mine after each outing.
- They allow you to fresh water flush your raw water circuit with the engine at rest without fear of overpressurization, because the water just runs through the pump.
You still need an exhaust system that drains the flush water out of the boat, which I have, so I also do this after each outing.
With over 25 years and 4000+ hours of service without any maintenance at all, I consider them good pumps.