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Mc-1 shifting issues

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bbsekiu

New member
I have a 70s model mercruiser 470 mc-1.

It will not shift into reverse with the upper cable attached.

But it will shift fine when I disconnect the upper cable and move the shift arm manually.

The boat did shift when I bought it. I replaced the bellows as well as the lower shift cable and now I'm having this issue.

I tried adjusting the lower cable to the 6in requirement in full forward but it doesn't shift into reverse with the upper cable attached.

Only when is disconnect the upper cable will it work.

What are the adjustments needed for the upper shift cable??
 
These adjustments are made with lower unit fully in gear & prop rotated until if locks. FWD adjustment will be rotated in 1 direction & REV the opposite. Lower unit tilted down until prop shaft is level & turned to basically straight forward. If either cable is worn excessively you may struggle to adjust. Also. If either cable is binding it won't be adjustable.

Starting point is LOWER cable @6" with slack pushed in & prop rotated to lock. Note 6" is center of hole to center of brass barrel.

Install lower cable with the anchor bolt in lowest end of slot (In other words, lowest = nearest the hinge point of arm)

Shift remote control to full FWD gear. While gently pushing LOWER cable in & prop rotated to lock in FWD, gently PULL slack out of upper cable & adjust it to connect to adjustment mechanism with the LOWER cable still pushed gently in.

Now, shift remote control to full REV gear. While rotating prop the other direction until it locks, slide anchor bolt upwards in slot until you gently pull all the slack out of LOWER cable. I would exect you will adjust the anchor bolt most of the way to the upper end of slot.

After making the final adjustment, verify with a helper rotating prop to lock that shift interuptor switch is not activated. Do this with FWD & REV. If switch is activating you are pushing/pulling too hard during adjustment.

When installing & tightening washers & nuts on the anchor studs just lightly snug the nuts then loosen approx 1/4 turn so you can rotate the washers under the nuts. This will verify cables don't bind on anchor studs.
 
To clarify the above adjustment procedure is for "short slot" units.

I would like to add that earlier MC1 units (about 1971 or 72 and earlier) had a long slot in the reverse lock valve arm. This is the slot I talk about in the 3rd paragraph above.
The longer slot was perhaps 2" long. The shorter slots were perhaps 1" long.

Long slot units started with lower cable adjusted to 5 7/8". Short slot units start with 6".

Without going into the geometry and radius of the slot detail to explain the difference.... There was also a slight difference in overall travel of the shift clutch and so the longer slot was required to get more cable travel.

Bottom line is use the correct initial 5 7/8" when adusting long slot units & 6" when adjusting short slot units.

Since the 470 came out in 75 or 76 timeframe I know his 6" starting point is correct.
 
Another thing when adjusting long slot units:

While I can't be sure if all long slot units but for certain some (and I believe most if not all) have a hole in the middle of the interruptor switch operating V shaped lever cam. This hole is to thread a generic bolt thru and into the female threads behind thus locking the cam in a neutral position. This helps made the adjustment procedure more accurate. Bolt is removed after adjustment but before final verification.

Am I going too in-depth? Maybe but cable adjustment is often misunderstood.

1st model year (1963ish) MerCruiser was simply MC1. It was a 14" prop diameter gearcase adapted from an outboard. It used the spring loaded outboard shift mechanism. I've never worked on 1, so I don't know if anything above is pertinent or if any are even still on the water.

Next came the MC1 A, B, C (1964ish). The A B C referred to gear ratio. This was an all new 16" prop diameter gearcase. There was no shift interuptor but if I recall they used the long slot mechanism.

Next came MC1 A, B, C with E-Z shift (1965 & 66). Same as above with the shift interuptor mechanism. Definitely used the long slot mechanism.

MC 120/160 came in 1967 and is the basic design used until 82. Long slot until the 71/72 timeframe then short slot going forward. This is where the long slot/ short slot initial measurment must be evaluated before starting. Going forward, the short slot procedure was used all the way to the Alpha gen 2.
 
I was able to adjust the lower shift cable stud to the furthest rear (aft) of the boat. I wasnt getting enough tension on the cable to stay engaged in reverse.
I will do an in water test to verify the problem is gone.
 
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