TheMagicWrench
New member
I have a 1973 6 hp Johnson 2-stroke engine (model 6R73S) that surges under load. I bought it second hand about 8 months ago in decent condition. For a little while I have had more difficulty starting it and it does not idle well at low idle. Then last week I took it out and while under way it started to bog down and slow. With the throttle kept wide open, it will spend 10 seconds to up to a couple minutes moving slowly and then surge up to a higher speed and stay there for 10 seconds to a couple minutes. I haven't noticed any pattern. I tried pumping the primer bulb with no effect. I also put it in neutral a few times and had no problem reving it and maintaining a constant RPM. I supposed that there was a fuel delivery problem, and so after that trip, I rebuild the fuel pump, and it started up easier than before and also idled much better. But when I took it out today, I had the very same problem with the engine surge/bog. The gas in the external tank is fresh and has oil and stabil in it. Any suggestions for a next step? I am thinking to rebuild the carb, but I wonder if there are something else I should check first.
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