557HG impeller, 6 or 10 blade?

[skid_marx]

New to outboards, but I've found this furum to be very informative and helpful so far. Got about 2 hours run time into my recently aquired pontoon, and so far I've had to replace a battery, and the water pump. Luckily I was smart (or lucky enough) to shut down when that mysterious buzzer started sounding. Anyway, after a bit a searching I ordered an impeller from Mercury, a 6 blade, and was quite surprised to find the old one was a 10 blade. Spoke with a couple different marinas and it seems they do not agree.
I see on an old post that claim both will work in my 557HG motor, but does one work better than the other? Boat is a 22' pontoon that will likely see a lot more low rpm hours than high. Opionons??

 

[Frank Acampora]

Re: 557HG impeller, 6 or 10 blade?

Counter-intuitively, the 6 vane impeller will pump slightly more water when it is operating as a displacement pump at low speed. This is because there is more open area between the vanes. The amount of difference should be slight, you would not notice, and I have never measured the difference.

At high speeds in cenrifugal mode they should both pump about equally.

UPSHOT: Use whichever one you want to use.

 

[skid_marx]

Re: 557HG impeller, 6 or 10 blade?

Thanks for the help. The 6 blade seems to fit better, certainly snug, have to bend the blades, but not as tight as the 10 blade, and it's about 1/3 the cost. So I guess I'll give the 6 blade a whirl. Thanks again.