1968 impeller 20 hp jhonson

[nightprowler]

Hello I picked up a 1968 20hp johnson it started up one pull i had it submerged 2 things, one there was water in lower unit i drained that the other is it was not pumping water air was coming out the hole but no mist no water. i only ran if for about 3 minutes. i ordered a new impeller so i dropped the lower unit but the impeller looks new!! this is my first impeller job seems easy enough but then again the impeller looks great. does it need to be in gear to spray or maybe warmed up? idk older unit any advise please help I'm so tired of putting around with a 9.5hp motor. and the fishing is great right now i just need the extra speed to get up river faster to work more shore
thanks
Tony