96 johnson 150 faststrike control issue

While throttling up or sometimes down, the engine cuts out intermittently. I've checked the neutral safety switch on the throttle and it checks out ok... no broken wires and the switch is working correctly. There appears to have been some type of lithium grease on the shifter controls at some time, but it's some what dry. Although the shifter moves pretty easily. Now the boat doesn't get used all that often, but I run the boat on a hose for about an hour about every three weeks and the boat is under a carport. Am I missing something and is it something I can fix?
Thanks!