Evinrude 90 v4 randomly runs rough

[Ralfirecapt]

I have a 1988 Evinrude 90 V4. The other day it started as it always does. I ran it for about a mile to a place we anchor out and swim. It ran great. We stayed anchored for about three hours as normal and got ready to head back. It started perfect and idled normal. When I engaged forward and tried to give some throttle it began to run rough and cut off. It would start back up easily, but still would take no throttle. I finally shifted forward and began idling in. After about 5 minutes of idling in, it began to smooth out and allowed me to give throttle and ran great all the way back. The next day we ran back out to our favorite cove again and it ran perfectly. I started it up to leave a few hours later and exact same scenario as yesterday. Any ideas.