140 Straight 6 control box calibration

[MercNdude]

Just got a 140 hp late '70s Merc and ran it on flusher muffs. Neutral for starting revs engine to pretty high RPM - I drop it back immediately for lower idle. I reset the lever to control lower idle at neutral for starting. I can't seem to get her to go into reverse when I pull back from neutral though. No matter what I do, I end up killing the engine before it will find reverse. A) How does the shifter work for forward-reverse? B) What is the relationship of RPM-to-shifter position? Aside from this... the engine is a peach. It hadn't been run for over two years and popped on the first try with good battery and fuel. Amazing. Started on the next try, smoked a bit and then smoothed out.

 

[ZmOz]

Re: 140 Straight 6 control box calibration

I'm not entirely sure about your problem, but I had a similar one with my 150...<br /><br />First, you should open up the controller box. Inside there is a cam that the lever moves back and forth, and this cam wears out causing the throttle/shifting to be out of adjustment. I got a replacement from a mercury dealer for $26. <br /><br />There is also an adjustment of the cables where they attach to the motor. It's hard for me to explain, but it's not hard to do once you loook at it. The 'thing' that holds the cables (shift and throttle) can be removed and spun around a few times to shorten or lengthen the throw of the cables.<br /><br />I ended up having to do both of these on my boat when I bought it...

 

[MercNdude]

Re: 140 Straight 6 control box calibration

Thanks. I've opened the box and I think I saw the cam you're talking about. I'll start looking for one. At that price, it couldn't hurt to replace it anyway! By the way, I don't know for sure, but isn't neutral in the center, reverse pulled back toward the stern and forward pushed past the center and toward the bow? Just checking. How far should I have to push the control past center to get fwd or reverse to kick in? Also, is the Mercury 1400 140hp a electro-magnetic shift or mechanical inside the lower unit?

 

[Clams Canino]

Re: 140 Straight 6 control box calibration

Before blaming the box. Disconnect the throttle / shift cables at the engine and try it all manually, also adjust the idle screw on the arm.<br /><br />Then re-hook up the cables (with controller in neutral) with the shift cable *just* favoring the reverse side of the "slop" and the throttle cable *just* putting a little pressure on the controll arm toward idle stop.<br /><br />It's best that you get the manual and check out all the timing and syncronization. <br /><br />-W

 

[MercNdude]

Re: 140 Straight 6 control box calibration

Good thoughts. Can I do the check with the key off? If so, I expect that in reverse, I should feel a lock on CCW rotation and in forward the lock should be against CW rotation. Also, at the engine, the upper cable is the throttle/shift cable right? The lower is the shift lock-out right? Thanks.

 

[Clams Canino]

Re: 140 Straight 6 control box calibration

Reverse will feel locked both ways. Forward will ratchet. Have someone turning the prop when doing reverse - the motion is required to make it go in.<br /><br />Yes the top one is the throttle.<br /><br />And it's hard to set the idle with the motor off. <br /><br />-W

 

[arboatdr]

Re: 140 Straight 6 control box calibration

Might want to take a lookat the shift shaft where it joins the lower unit. I've seen a number of these that were corroded almost to the point of breaking that would twist rather than operate the stiff reverse lock on this engine. If your cable bottoms out with no reverse adjustment this would be a good place to start.

 

[MercNdude]

Re: 140 Straight 6 control box calibration

So someone should turn the prop to sync in reverse? Ok. Never dropped a lower unit before. From comments I take it this is an easy thing to do. Do I need to get any seals or such in advance? Thanks a heap! You guys are very generous to help out a new MercNdude!

 

[ZmOz]

Re: 140 Straight 6 control box calibration

I took off my LU for the first time a couple days ago. The hardest part was going to two hardware stores to find a socket that fit! If your drive shaft is rusted, however, this can be a very big project.

 

[MercNdude]

Re: 140 Straight 6 control box calibration

To all! Success! Thanks for your help. I ended up having to drop the L/U and rotate the gear at the base of the shift shaft 180 degrees. That way, it only had to be turned about a half inch before neutral led to reverse. W/O turning it, the whole gear had to rotate several inches around before reverse could engage. The cable didn't have that much throw in it. I tested her today, engine running, and got fwd-neutral-reverse. I owe you guys one! MercNdude