1976 6hp runs rough....sometimes

I have a 1976 6hp Evinrude long shaft outboard on my little sailboat. It has been running great since I replaced the impeller and went over the carberator two years ago.
This past month I took it out, and ran it for about 30 minutes. I sailed for about an hour without the engine, and then started the engine up again. This time, it would not reach its full RPM's and sounded like it was going to die at any moment.
I have repeated this several times. The last time I did not think I would make it back to the dock, but when I put it into neutral, it ran back up to full speed. It then worked fine in reverse, but shut down in the forward gear.
It has fresh gas with stabil and oil, I allow it to run without gas until it runs rough after each outing, and starts cold easily.

Any ideas on my problem?

Re: 1976 6hp runs rough....sometimes

did it sit all winter until this last month. if so the carb probably need some attention. you are not running it completely dry. to do that you run till it quits. this is not as bad on single carb motors, as it is on multi carbed motors, as both cylinders run out of gas at the same time with a single carb.

Re: 1976 6hp runs rough....sometimes

I ran it in October, February, March and May. It just developed these symptoms this past Month (early June).

Re: 1976 6hp runs rough....sometimes

Well, I rebuilt the carb and took it out this weekend. It is not perfect, but it is running a lot stronger than it did before. I'm going to try to run it a bunch before the end of the season.