Re: 1986 Johnson 70 rough idle and at lower RPM
Not normal -- you should be able to get that motor to idle smoothly all day long if you need it to. The only harm I can think of that might result from running it like that is, it might melt a piston. Other than that, should be ok.
sorry, jus kidding, seriously though, remember that your motor gets its lubricating oil from the gasoline, so if you suspect fuel starvation, the worst thing you can do is keep running it.
In the future, to save yourself the trouble of swapping coils, get an inline spark tester (couple bucks at autozone), set the gap to 7/16", clip it to the engine block, attach the plug leads (one at a time), and look for strong blue spark while cranking. If it can jump a half inch gap in the open air, it'll fire in the hole.
Loose throttle cable will cause erratic idle. Take a look at the idle set screw; it needs to be butted up against the throttle lever when the throttle/shift control is in the neutral position. If it's not, use that black thumbwheel to adjust the cable length, to where you can set the idle speed at around 850-900 RPM, in gear pushing the boat. On the muffs, set it to around 1000 then fine tune it at the lake.
If that doesn't straighten her out, a carb rebuild is an excellent idea. Install new kits. Follow the "carb cleaning and rebuilding" link from the "top secret file" at the top of this forum for good tips, including instructions on fabricating a jet removal tool.
