Late 70's 35hp evinrude

[bobbyjadams]

I have a late 70's model 35 hp evinrude. When I first got it every time I started it for the first time of the day it would barely run above idle speed at full throttle then it would jump up and take off after about 5 or ten minutes of running like that. The last 2 times I have taken it out it will not "run up" to speed at full throttle it just idles down and putters along at slightly about idle speed like it used to first thing in the morning. I thought I mixed my gas to rich so I poured out that tank and started with new gas and changed my spark plugs (gapped at .040) and still same problem. It also is having a hard time starting like it is not firing. Thats what led me to change my gas and plugs. Any help would be appreciated.
Thanks
Bobby