Twin Johnson 70s...can"t get idle below 1400-1500rpm.

[kentuckydiesel]

1974 and 1981 Johnson 70s.
Bought the boat a couple weeks ago and did the normal stuff including carb cleaning before taking it out on the water to test. In neutral, both engines were running about 2000rpm (supposed to be 1000rpm according to the Johnson service manual) Went through and did all the carb linkage/cable adjustments according to the Service Manual and ran both engines on muffs. Can't seem to get either engine down below 1400-1500rpm.

All adjustments are correct, carbs are synced, throttle butterflies are closed all the way, both engines putting out a healthy stream of two-stroke smoke at idle (so I don't think they are running lean).

Any thoughts? I just hate putting the lower units through stress of rpms being any higher than they have to be.


Thanks,
Phillip

 

[kentuckydiesel]

Re: Twin Johnson 70s...can"t get idle below 1400-1500rpm.

Nobody? Next step for me might be opening up the low jets. Input appreciated.

-Phillip

 

[Silvertip]

Re: Twin Johnson 70s...can"t get idle below 1400-1500rpm.

Does it make sense that opening the low speed jets will lower idle?? That will certainly make it run rich. While you say the adjustments are correct, they obviously are not. Idle "speed" on a two stroke is controlled not only by the carburetor but by the ignition advance as well. So all of the adjustments including link & sync should be done with the throttle cables disconnected. You may have the carbs set right but the advance system may not be. The throttle cables should be adjusted last.