1974 evinrude 70 hp impeller question

[Woods Before Water]

Ok been a while since I've been on here. Well I'll get straight to it. I've got a 1974 starcraft holiday 18' with a 1974 evinrude 70 hp main motor. I just did a new water pump install. I started the motor with the thermostat housing off in a trash can filled with water. Motor runs excellent and seems to be pumping water but it seems slow to pump. It runs for about 1 minute or so before water starts flowing out the t stat housing. My question is tgat if this is normal. Never had a motor without a pisser tube. Also I know there was a topic about installing a pisser tube. Is like to do this while I have the housing off, if someone could direct me towards the post. I've done a search and can't for the life of me find it. Appreciate any help. Thanks.

 

[interalian]

Is the water level in the trash can higher than the pump body? If not, it'll be slow to pump, or not pump at all.

 

[Woods Before Water]

Yes it's above both the intake side and the output sides of the lower unit. It's above the second fin on the lower unit