I understand the blue ones won't pump as much water.

I tried them once in my boat, it was years ago so the problem might have been fixed, but the brass hub slipped in the rubber after one blast at high speed. They do in fact run dry for a while, but I am afraid of them.

I change over to the new style also on my '94 Gen V 502 on my first replacement time. The old style had the water lines going out at a 90, where as the new one peice it goes straight out.

As far as the Blue impellors, I can see where the impellor might last longer when run dry, But whenever my Merc ones have ran dry, from stupidity, it also ruins the housing. Just a consideration.