SCANDINAVIAN

Just changed my impeller and O-ring last week (Mercury). When I started it up I tried to run it with a hose directly from the pump inlet to a bucket filled with water but there were no suction at all. Took the hose out of the bucket and connecting it to a hose with water pressure and I got great water flow through the engine. When I disconnect the water pressure hose the pump have great suction and when I quickly put the hose connected to the pump inlet it back in the bucket it works perfectly, but if I stop the water getting in the hose with a finger or lifting the hose out of the water just for a second or two suction stops. I read a few threads before changing the impeller and checked for grooves in the endplates but the they were smooth. I have checked for airleaks but havenīt found any. Can the two air hoses connected on the top of the pump have something to do with this problem?
Thanks in advance! Engine is 2005.

Expensive Date

The two top air hose's are part of the air purge system. If they are broke, or missing pump will suck air. 496's don't like to pull water from a low source, where is this bucket? You may not even have a problem.

SCANDINAVIAN

Thx Expensive..I had the water level in the same level as the waterline so it must be something else. I checked the air hoses and they also seem to be in good shape. Have the pump off and in pieces again, double checked the endplates but they are smooth, O-ring and impeller is intact and all surfaces flat and clean.
I have been running on a hose this way numerous of times and the pump has never been sensitive to the small air leaks I know I had when connecting the hose, not even with a very old impeller. Now, with a new impeller and without those air leaks I have no suction. I also installed a new serpentine belt and it is not slipping.
Running out of ideas...

Naughty Kitty

No easy way to check the end clearance between the impeller an the housing cavity without a caliper...with the impeller fully seated in the housing, place a straight edge across the impeller and make sure it is flush with the housing. Video link below is for a 496 pump rebuild, but the 5:00 minute mark shows what I am talking about.

https://www.youtube.com/watch?v=oqnV-FJhRvg