1979 70hp johnson -- not enough throw in gearshift

[Dabbler_E]

Replaced lower unit, and I've had trouble getting it to engage both forward or reverse without skipping. I can adjust to get one or the other solid but not both. Seems like the shift lever isn't throwing far enough to really seat the clutch dog both ways. Can this be fixed by tightening/loosening the shift cable, or could it be due to the shift rod height not being quite correct?

Thanks

 

[Daviet]

Re: 1979 70hp johnson -- not enough throw in gearshift

There is a lenth adjustment for the shift rod. You will want to get a factory manual to help with the adjustment process.

 

[noelm]

Re: 1979 70hp johnson -- not enough throw in gearshift

you may well have not adjusted the shift rod correctly, but the way I see it, that adjustment (unless it is way way out) only makes a difference to the position of the shift lever on the motor, your control and cable will still move the lever to engage forward and reverse, but the motor mounted lever will no longer be perfctly vertical when in neutral, am I correct in this thinking? your problem is a very common one and I have yet to find anyone who has a 100% solution, do a search and you will find a heap of posts on this.

 

[crxess]

Re: 1979 70hp johnson -- not enough throw in gearshift

Normally a stretched cable will cause Reverse but no forward. By adjusting to try and correct, you can loose both. Disconnect the cable and manually shift. if it works, get a new cable.

Once a cable is stretched it is useless.

 

[jtexas]

Re: 1979 70hp johnson -- not enough throw in gearshift

from your OEM shop manual:
"k. Turn shifter until it seats in shifter detent. Then back out about 3 turns until top end offset faces ports side. Shift into NEUTRAL. ... The distance from the top of the gearcase to the center of the shift rod hole is 21-23/32" +/- 1/32". ..." I've not had any problems measuring with an ordinary tape measure.

I doubt that's your problem though, if you can get it into forward and neutral both, with the shift rod connected up under the carbs.

Did you disconnect the shift cable from the bellcrank and walk through the cable installation procedure in the manual?

The shift cable trunnion nut is where you adjust the cable throw to make it shift into forward & reverse at an equal distance from neutral.

 

[noelm]

Re: 1979 70hp johnson -- not enough throw in gearshift

Normally a stretched cable will cause Reverse but no forward. By adjusting to try and correct, you can loose both. Disconnect the cable and manually shift. if it works, get a new cable.

Once a cable is stretched it is useless.

and just how exactly can you lose both by adjusting? the plastic adjuster nut adjusts the inner to outer length ratio, so a stretched cable can be compensated for by a simple turning of the nut. This fault has been covered a dozen times, and a solution is yet to be found (or at least found and revealed to all)

 

[crxess]

Re: 1979 70hp johnson -- not enough throw in gearshift

and just how exactly can you lose both by adjusting? the plastic adjuster nut adjusts the inner to outer length ratio, so a stretched cable can be compensated for by a simple turning of the nut. This fault has been covered a dozen times, and a solution is yet to be found (or at least found and revealed to all)

Maybe someday I'll get to look at one of these mystery problems and get a better understanding.

Anyway, my apologies. the cables on my bigger boats do not have outer casing adjusters. they are pre-fitted design with specific connectors on each end. Normally good for many years use, but can fail if not maintained properly.

It would seem to me the first thing would be to Manually shift and confirm function. then to work backwards to the control box.

i.e. if the lower unit shifts properly, manually at the motor, the next step would be to attach the cable at the motor side only. Manually work the cable and watch the throw to confirm proper movement and gears engaging. If this works properly, verify the full length of cable movement from reverse to forward.

Next you would be able to examine the shift box and verify length of movement. Condition of bushings. Slop in the handles, etc.

 

[noelm]

Re: 1979 70hp johnson -- not enough throw in gearshift

I will bet he can shift manualy at the motor and get both forward and reverse, I have seen this problem a couple of times, and one of my motors has the fault and I cannot see how to fix it, motor works fine shifting by hand, cable is new, you can adjust for forward and neutral, or reverse and neutral, but not both, as soon as someone comes up with a fix a lot of people will be very pleased. I have looked at both control boxes and they both appear the same (I did swap them over) and the fault is still there.

 

[Dabbler_E]

Re: 1979 70hp johnson -- not enough throw in gearshift

To clarify: shifting manually with cable disconnected works fine -- it engages forward and reverse solidly. My problem seems to have been turning the trunion nut the wrong way, which reduced the length of throw. At least by hand turning, I can get hookup (turning the prop causes the flywheel to turn) in both directions . Haven't tested it under power yet.

I'll let you know how it turns out.

 

[ezeke]

Re: 1979 70hp johnson -- not enough throw in gearshift

Sometimes it gets more complicated; check this thread to the end: http://forums.iboats.com/showthread.php?t=326160&highlight

 

[Dabbler_E]

Re: 1979 70hp johnson -- not enough throw in gearshift

Finally tore the gearcase apart after half a year without reverse gear.

Clutch dog and reverse lobes were both highly worn, but the ultimate cause was a spacer ring that was supposed to go between reverse gear and the clutch dog, but I had installed on the other side of the reverse gear. D'oh! That error caused there to be a lot of end play in the prop shaft, so I could only adjust the shift cable to get one gear or the other, but not both.

Fortunately, I had a spare clutch dog and reverse gear lying around (from a LU whose driveshaft roller bearing had fried).

Back up and running, snapping into both gears with authority!