I changed out the lower unit on a 70 johnson, can't get the shifting adjusted.
Should the shifting rod be turned out so many turn or can I make adjustment with something else.

There are several issues that can cause this type of problem and subsequent solution. First lets take a look at how it shifts and and the basic set up. When all things are in order, under the carburetors is a special screw that had to be taken out to remove the lower unit. This screw is connecting the shift rod from the lower unit to the shift lever. (Newer style has a hair pin and you slide the shift lever over to release the shift rod) In either case this lever is orientated straight across when in neutral and the part of the shift lever that is connected to the shift cable is straight up and down.
The procedure in the manual will have you measure the shift rod height with the lower unit removed, the measurement is from the center of the top hole to the top of the lower unit mating surface next to the shift rod seal housing. This can be done with a ruler or there is an expensive tool from OMC to accomplish this procedure, and the distance is dependent on year model and shaft length of the engine.
You could screw the shift rod to about the center of its possible insertion while the unit is off, then install the unit and check for the shift lever location, then remove the lower unit and make an adjustment accordingly. This will be a long way of achieving your goal but will work.
Also for other reasons of your difficulty could include, several worn shift parts, this system won't tolerate much wear or slop in the system. Could be, depending on the specific difficulty, that the control box, cables and levers of the system are worn and some bushings need to be replaced. Should you give me the model number and specific problem your having I could help further.
The parts diagram below is for a 1985 Johnson 70 and utilizes the "Hairpin" (#87)method of shift rod retention. The lever #99 should be straight up and down when all pieces are together and lower unit is in neutral detent.
Picture of a 1988 70hp Johnson
The hair Pin is # 87 - To release the lower shift rod.
The Lever #88 - Should be straight up and down when all pieces are in place and shifted into neutral.
The Lever #28 and #69 attach to the lower shift rod and should be at a 90deg location to the Lever #88 when all pieces are in place and in neutral.
Added: Just got a measurment for you 21-23/32 inches, Measure from the center of the Lower Unit shift rod hole Center(#50) to the top of the lowerunit housing (#1), while in neutral detent. Install the unit and check for the position of the shift lever.

I have a 1972 Glasstron V166 with a 100 horse Evinrude. It has three buttons on the throttle control for forward , neutral , and reverse. When I put it in reverse it jumps in and out of gear. Everything else seems fine. Is there an adjustment or could it be an electrical problem? I just bought the boat so I don't know any history. Thanks! J.D.