96 speedster bilge pumps on land...not in water

[Cablebandit]

My 96 Speedster bilge will pump water like crazy when on land but not while in the water. I hear it running but the water level never lowers. I checked the hose and it has no leaks. Stumped at this point.
Water is coming in from a shaft seal but only while running on plane. I can let it idle all day long in the water and never get a drop. The leak is a seperate issue but first i must figure out why it's not pumping water out while in the water

 

[snikwad003]

I would hook a temporary hose to the pump and hold it over the side and confirm its not pumping because that sounds weird. Are you 100% you have no other leak, mine is leaking around the flush port only when someone is in the back right hand side of the boat.

 

[1983]

How much water is the pump seeing around it?

All of mine need to have basket part nearly submerged/surrounded with water to pump the water out.

 

[howie099]

for my bilge system to kick in I have to dump the like 5 gallons or so of water to get it to kick in. You can't heat those little pumps with the engine cover on and with the engines running forget about it. You will have water drain from them unless you keep the pump on a lot. Make sure you have a loop in the hose above the hull fitting so the water don't come back in and you make that little 1/32 hole in top of the loop.