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70 HP Johnson Idle Adjustment

7

70JohnsonNH

New member
Can someone please tell me which of these I should be adjusting for the idle?

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The bottom screw but you should do a complete link & sinc unless you are certain it is currently correct (read as in never tampered with since leaving the factory).
 
No & it's not normal for the cable barrel to be adjusted to near full travel only. Notice the shift cable is mid range.
Is this a new to you motor?
Is your idle too high or too low?
 
This was a new to me motor about 4-5 years ago from a guy at a local marina that had a lot of positive referrals when I reached out on a local facebook group looking for a replacement motor. He supposedly had the whole thing apart and did a rebuild essentially

The idle is definitely way too low. It can almost idle on a hose but absolutely will not under load in the lake
 
I never idled from day one. He mentioned tuning it in cool weather so in hot months might be tough running. But even in early or late months in the season it never ran/idled correctly. Which is dangerous when trying to dock, especially when trying to dock or get through a busy no wake channel

At this point I just want to adjust the idle up a little to see it will run better. If it dies within a season or two or three because I don’t do the link & sinc it is what it is
 
The following is not how to adjust your motor, it is a generalization of OMC procedures:
The "link & sinc" synchronizes the opening of the throttle with the timing advance. I'd take the throttle cable off before adjusting because it will be fighting you. Afterwards reattach the cable WITH THE REMOTE CONTROL IN NEUTRAL, adjust the barrel to fit onto the lever when against the idle stop screw.

The nearly horizontal rod with 90 degree bend aft to plastic stud reciprocal threaded on fwd is the 1st step. It's length is critical. If it's wrong the timing curve won't be correct. The geometry between the vertical lever & throttle cam depend on this initial adjustment.

All 3 carbs must be adjusted to fully closed together. The cam follower lever needs proper adjustment to the cam.

Carb idle mixture needs to be adjusted slowly & methodically with the engine idling & the lower unit at normal operating depth in a tank or lake. As this is happening, the idle stop screw may need adjusting. BUT the throttle plates in all 3 carbs are fully closed. Idle speed is adjusted by timing not carburetor throttle plates opening. There is no specific timing adjustment at idle, only a max timing at a specified RPM under load. Idle timing will be near zero degrees but may be a few degrees plus or minus.

The upper stop screw (sort of inline with center carb) gets adjusted to stop travel at carbs full open. Look at carburetor shafts & you should see roll pins that are near horizontal at idle & vertical at wide open. It is possible to move throttle levers further but that actually moves them past wide open thus starting to close.

All this is assuming your engine is in good condition and you are not putting make-up on a pig.
 
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