Re: 35 hp evinrude pumps good except when planing?
I really am glad you got it fixed and working. Honest. But I gotta say that of course you should install the vanes pointing the right way. However, I also gotta say that if you install them backwards, they will flip over as soon as you start it. Speaking of a NEW impeller here. I also gotta say that when the motor stops and bounces backwards off the last compression stroke, it may cause one or more vanes to flip over backwards, and they too will correct themselves when you restart it.
So, by taking it apart and doing the job over, you corrected whatever was wrong without realizing it. I have no idea what that something was. But it is fixed, so mission accomplished.
Before I end this post, let me say that I am talking about the motor in question. SOME motors with short stiff vanes may not correct themselves. But a 1978 35hp isn't one of them.