I just bought this boat about 2 weeks ago. The boat is a 1979 FM Marine Sunliner 19 ft. When I test drove the boat it ran fine. I went out on the water for the first time since buying it/testing it and it ran totally fine for the whole day. Then I went to take it out the next day and it ran fine for about 20 minutes and then the engine would start surging and it would jerk you forward in the boat. It doesn't surge until about 1200-1500 RPMS, but when I try to plane then it starts doing it. The boat then died in the water and would not start so we started rowing the boat back to shore. After 10 minutes of rowing we tried to start the boat and it instantly turned on and we were able to get back to the dock but it was still jerking.
I took the fuel line from the carb and put it in a jar and turned the engine over and it seemed to be working fine. I went ahead and replaced the fuel filter and fuel and water separator and ran some sea foam through the engine and filled up on Premium 92 Octane gas. I just took the boat out and it instantly started doing the same thing. I accelerated and it started surging every 2 seconds and then I turned back to the dock and it got worse and worse and then died again. This time I was able to start it again and got back to the dock. It idles fine and can run at low RPMs. The repair manual says engine surging is typically attributed to the fuel pump. Could it be the fuel pump even though it seemed to putting out gas? What else can I check and do? Thank you for any help and advice you can give me!