Hello. I recently bought a 1980's era Mariner 684 15HP. I saw it run in a bucket before purchase and it came with a parts engine. When I took it out for the first time, it seemed to run OK, except the RPM's fluctuated sometimes for no reason. Holding a steady throttle position, you could hear the engine speed up and slow down. As time went on, it got worse, and it also became hard to start. So, I started doing some routine fuel-system things, like replacing all the fuel lines, replacing the old screen filter with the disposable paper ones, did a complete carb clean/rebuild, rebuilt the fuel pump, new spark plugs, etc.
Took it out for the first time since the overhaul and it started on the third pull (forgot to turn on the kill switch for the first two) and it settled into a nice, smooth idle. Ran it this way until out of the no wake zone, when I came up to speed, the RPM fluctuations returned. I never had trouble restarting it, but by the time I got back, the formerly smooth idle was now lumpy and uneven, with the motor shaking somewhat as I idled along.
Just looking for advice about what to try next. Thanks in advance for the help.
Took it out for the first time since the overhaul and it started on the third pull (forgot to turn on the kill switch for the first two) and it settled into a nice, smooth idle. Ran it this way until out of the no wake zone, when I came up to speed, the RPM fluctuations returned. I never had trouble restarting it, but by the time I got back, the formerly smooth idle was now lumpy and uneven, with the motor shaking somewhat as I idled along.
Just looking for advice about what to try next. Thanks in advance for the help.