1978 115hp mercury shift problem

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Elliomcmh

Seaman
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Mar 22, 2011
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65
Hi, my engine will not go in reverse when shifted from the controls. I can undo the linkage and it will shift fine, from F N R, when manually shifting the shift rod. But when I hook the linkage up, even though the shift rod is hitting the same point, for some reason it will not even come close to going into reverse. Any ideas? Thanks
 
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Chris1956

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Mar 25, 2004
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27,137
Re: 1978 115hp mercury shift problem

Maybe you have a bad control, or the cable is not adjusted correctly. Release the cable from the clamp on the motor. Now set the control to neutral and set the motor manually to neutral. See if the cable will easily go into the clamp. If not adjust the barell nut until it fits the clamp easily. If that is not it, you might take the control box apart and look for broken/work parts.
 
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Elliomcmh

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Mar 22, 2011
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Re: 1978 115hp mercury shift problem

I'm about to give it a shot, thanks for your help
 
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CharlieB

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Re: 1978 115hp mercury shift problem

How OLD is that shift cable?

An old stretched cable will give you those same problems, readjusting may not solve the problem, a replacement cable is necessary. A new cable is cheaper than the cost of rebuilding a gearbox because the worn cable will continue to accelerate wear on the engagement dogs by not shifting firmly and completely into gear.
 
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Elliomcmh

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Re: 1978 115hp mercury shift problem

The cable has a date of 02' on it. I did unhook all of the linkage, and figured out that when manually shifting the shift rod from neutral to reverse(engine off), that it only engages when the prop is in certain positions. When the engine is running, and I try to manually shift it into reverse, it goes in every time. But never with the linkage hooked up Thank you for your help
 
merc850

merc850

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Re: 1978 115hp mercury shift problem

"Due to the design of the shift mechanism the motor should only be shifted into reverse while running or you can damage the shifter" - it says in the manual.
 
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Elliomcmh

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Mar 22, 2011
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Re: 1978 115hp mercury shift problem

Ok thanks for that very important info merc850, I'm definitely glad that I know that now, that sheds a little light on things.
 
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Elliomcmh

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Mar 22, 2011
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Re: 1978 115hp mercury shift problem

What's the best way to figure out what size/model shift cable? And, can anyone recommend a website to order one?
 
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Chris1956

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Mar 25, 2004
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Re: 1978 115hp mercury shift problem

Mercury control cables are avail at most marine stores. Find the number on the cable to get the length, or go on the Teleflex website and find the formula to determine the length of the cable needed.

Are you sure it is a cable issue?
 
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Elliomcmh

Seaman
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Mar 22, 2011
Messages
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Re: 1978 115hp mercury shift problem

Chris1956 said:
Mercury control cables are avail at most marine stores. Find the number on the cable to get the length, or go on the Teleflex website and find the formula to determine the length of the cable needed.

Are you sure it is a cable issue?
Click to expand...

I think that's what it is. Several people recommended that I try that first. Is the control mechanism hard to take apart? Do you have any other suggestions what my problem could be, if it's not the cable?
 
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Chris1956

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Re: 1978 115hp mercury shift problem

I have never had a stretched cable. I cannot understand how that would be an issue. Why not measure the travel the cable goes from neutral to forward and from neutral to reverse and see if they are the same. If not, it is likely a control box problem.

The bod comes apart with two screws. it is a bit complicated, so take your time.
 
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Elliomcmh

Seaman
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Mar 22, 2011
Messages
65
Re: 1978 115hp mercury shift problem

Chris1956 said:
I have never had a stretched cable. I cannot understand how that would be an issue. Why not measure the travel the cable goes from neutral to forward and from neutral to reverse and see if they are the same. If not, it is likely a control box problem.

The bod comes apart with two screws. it is a bit complicated, so take your time.
Click to expand...

I am going to measure it. I do know that when the controls are in the reverse position, the linkage is all the way to the rear, and the shift rod is in the correct position to shift the motor into reverse, because I can manually shift the engine into reverse in this same position with the linkage undone and the engine running.
 
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Chris1956

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27,137
Re: 1978 115hp mercury shift problem

It is possible the upper and lower shift rod are out of alignment, as they can fit together several ways. When the motor is in neutral , the shift slide should be in the middle of it's travel.
 
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