cam and roller adjustment 70's era 70HP??

[bid_360]

I have a 70 HP Johnson motor mid 70's I think. I am less than a novice when it comes to motors. But anyway, I need a little help...
The motor idles great but doesn't seem to be opening up all the way. On the water doesn't even plane out of the water. I have attached photos to illustrate what I think the problem is.
First photo - throttle in neutral
Second photo - full throttle with the throttle lever
Third photo - cam can move this much further.

Can I adjust the cam to push this roller all the way down? How can I and should I? It almost looks like I can adjust the cam somehow to extend it out to where it could hold the roller down as far as pic 3 shows.
Any help would be greatly appreciated.
Thanks,

 

[Topol_86]

Re: cam and roller adjustment 70's era 70HP??

I've got a 1978 70hp, just pulled the carbs to do a rebuild, I noticed that the throttle plate actually rotates farther around to almost closed position if turned, look inside the carb with the throttle at full and see if the plate is sitting flat (as to not restrict any airflow into the motor) the first one you see will be the choke, look further behind it for the throttle. On my motor I have an air breather box attached to the carb, if you have the same you'll need to remove it to gain visibility.

 

[willamettejeff]

Re: cam and roller adjustment 70's era 70HP??

I have a 1978 70hp Johnson. Your throttle is only half opening. To get started disconnect the throttle and gear shift cables at the motor end just to take the controller out of the equation for now. It looks from your 3rd picture that the throttle plates will fully open when operated manually, so the problem is that the cam is not rotating far enough. With the cables disconnected can you rotate the throttle arm to get the cam to rotate far enough or is it stopped by the upper throttle stop screw too soon? You may have to rotate the prop to get into gear before being able to fully move the throttle arm. If stopped by the stop screw can it be adjusted enough to allow the cam to rotate far enough?

A picture showing the whole mechanism at idle and one as far forward as it will go would be helpful at this point.

 

[ezeke]

Re: cam and roller adjustment 70's era 70HP??

When the throttle arm on your control is in the idle position and the warmup lever is down, the cam roller should be exactly aligned with but not touching the lower raised mark on your cam follower. At this time the carburetor throttle plates should be fully closed.

If the throttle plates are not fully closed, disconnect the throttle cable, synchronize the carburetors, then adjust the cam roller to the mark.

When the carburetors and roller are correctly aligned, adjust the throttle cable to the throttle lever so that it slips on without moving the lever.

The throttle plates should be fully closed at idle, horizontal and no more than horizontal at WOT, and perfectly synchronized throughout the entire range of motion.