Reply To: Big or Small water pump impeller and housing?

[Don]

mike n wrote:

i believe the newer style impeller is taller,so it might not be that much smaller. i installed one on a 5.5 and didnt put too many miles on it but didn’t see any problems

I would agree.  The taller height of the new style impeller compensates for the lack of diameter.   Keep in mind, the impeller only tells half the story here.  The wear of the older aluminum housings is often over looked/missed when replacing impellers.  The SS liners on the newer style pumps seem to wear less than the aluminum housings.  I would not be concerned about possible lower water pump output when replacing the old style set up with the new style.

I used to use a relatively simple test when servicing older motors with the aluminum pump housings while running in a test tank (not a barrel).   Just let the engine run in neutral or reverse at high idle for several minutes.  A worn pump would usually start reducing pump output slowly after a few minutes, but output would return to normal once back in forward gear taking advantage of water being passed by and directed into the pump inlets.

The one short coming of the plastic housings shows up in salt water though.  Salt seems to make its way between the plastic and the SS sleeves for the housing screws, splitting the plastic open around the sleeves.  You can’t use a torch to loosen stuck screws without igniting the nasty plastic as well.  But, there is no excuse for not cleaning and lubing impeller hsg retaining screws properly during service either.

So, in the end, I would not have a problem using either style set up on an older engine.  Just stick with OEM parts/kits,  I wouldn’t trust most amazon/chinese aftermarket “stuff”.