1958 johnson 7.5 AD 12 high and low speed levers

SPK

Seaman
Joined
Nov 21, 2010
Messages
55
Hello again,
I have read Joe Reeves' post regarding setting the high and low speed needle valves on older motors like mine and it is really informative.
My question is about the high and low speed levers[plastic knobs] located on the cover plate.
I am trying to figure out where one should set them initially, realizing that they are able to be dialed from 1 to 6 on the slow[lean to rich] and the reverse number order on the high 6-1[rich to lean].
A the base of each lever is a small piece of plastic that juts out[moulded as part of the lever],[like a little "stop arm"] I asume as a reference point in adjusting rich and lean.

The cover plate at the slow speed lever has a moulded plastic stop that sticks out of the cover plate approximately in the middle at the top. The slow speed lever makes contact with this little outcropping when you turn it.

The cover plate at the high speed lever has no plastic stop that the high speed lever can come in contact with. It does not appear to me that there ever was a stop on the cover plate at this location.

The slow speed lever points in a downward direction and the high speed lever points in an upright direction.

Is there a position that I should set these two levers at initially in order to adjust while running.
I assume that in the middle would give me equal rich/lean adjustment by turning right or left according to the dials.
One thing I did have to do was tighten the packing nuts for both needles as they were loose. On my first test run with the motor on the river, the high and low levers were moving due to the vibration of the engine. After reading in the forums here I carefully tightened them as per instructions making sure that the needles themselves did not move as I tightened the nuts. This procedure really improved things for my second run on the river. I could do some adjusting on the levers and get her running pretty good.

One thing I am noticing as I run the motor is that I can troll along at quite a slow speed while fishing[for easily over an hour] but when I go to speed up to return to shore, the motor does not accelerate right away but in about 15 seconds cuts in and speeds up to top speed. It does not die out or stall, it just doesn't rev right up right away like it should. You would think perhaps it was getting too much gas all at once and taking a few seconds to adjust to the increase in fuel. Once it kicks in and speeds up it maintains this speed until I am at the dock.[runs like a champ back to shore]

Currently the setting on the slow speed dial is about 3 1/2 and on the high speed dial about 4 1/2. Based on how the motor runs overall, I don't think I am too far off the mark in my settings but then again I don't pretend to know a whole lot about these motors. I am just learning.

Do you think that running 2 oz. of Seafoam per gallon for a tank or two or longer would be a good idea?
The motor doesn't run too badly overall but I don't feel too confident about removing the carburetor and getting in over my head which in the end might end up making matters worse.
I look forward to the experts weighing in on this topic.
Once again, I read forums on here almost every day and this is indeed a wonderful site.
Recently I got a copy of a parts manual from Ebay and I have the Old Outboard Motor Book as a reference. As yet I haven't been able to secure an owner's manual but I don't know if it would have a lot of information in it.
Looking forward to hearing from you.
Thanks,
Sean.

I have great pressure on the 2 line tank and have replaced the o rings in the line fitting[no leaks].
 

samo_ott

Vice Admiral
Joined
Jun 18, 2006
Messages
5,125
Re: 1958 johnson 7.5 AD 12 high and low speed levers

First of all, don't be concerned about taking the carb off. They are VERY easy to work on. There's just a few parts in there. And if you really mess up (which is hard to do) just post your problem and there's score of folks here that will help you out. And since you have the parts manual you can see how it goes back together.

As for the low and high needles. The numbers mean nothing. They are relative positions only. To start off turn both screws in all the way until they stop. Do this gently. You might have to push the plate in so that they can fully turn and not hit the stop tabs. BTW, these stop tabs are a nuisance and I'm not sure why they are there as they restrict the full turning off the needles. Then once fully in, back out the slow one about 1.5 turns and the high speed one about 3/4ers of a turn. This is the initial starting point., Then fine adjust as needed. And yes, the packing nuts collars must be tight so that the needles can just turn.

Keep posting if you have more questions, as mentioned, there's lots of help here... Have you changed the impeller yet?
 

SPK

Seaman
Joined
Nov 21, 2010
Messages
55
Re: 1958 johnson 7.5 AD 12 high and low speed levers

Thanks Steve,
Do you have to loosen the packing nuts before turning the high and low needles in gently to seat?
No I have not changed the impeller as she seems to be putting water out pretty well.[I hope I don't have to get into that project}.
Thanks,
Sean.
 

samo_ott

Vice Admiral
Joined
Jun 18, 2006
Messages
5,125
Re: 1958 johnson 7.5 AD 12 high and low speed levers

The packing nut collars should just be tight enough so that you can turn the needles (and there is some friction) but that they are not loose or can turn themselves and then leave them that way. Also, once the 2 needles are adjusted properly they should not be need to be adjusted again. If you want, once they are adjusted properly, pull the knobs off and put them both back on at the 12 o'clock position. A lot of folks do this thus they know exactly where they should be if they get hit or accidently moved.
 

SPK

Seaman
Joined
Nov 21, 2010
Messages
55
Re: 1958 johnson 7.5 AD 12 high and low speed levers

Thanks again Steve,
I have set the needle valves and tested the motor on the water. The fine tuning is getting closer. I found that I had to make sure that the high speed adjusting knob was pointing with the tab to the 12 o'clock position because if it was pointing straight down, I could not put the hood back on. You know what you are speaking about. I like the idea of having them sit pointing either straight down as is my case for the low speed knob and straight up in the case of the high speed knob. I can remember this by the old saying "speed up and slow down".
You did mention to me about the impeller in your earlier post. I guess this is an issue I will have to deal with eventually. I do not know if the impeller was ever changed on this motor or not, I assume by the year of it that it must have been changed at some time. I watch for the water stream as I run the boat and so far it is putting out water. Do you know of a good thread that I can read with clear instuctions to follow when I decide to tackle this job. Is this information in an owner's manual for this motor? I don't really wish to purchase one if it doesn't have much technical information in it. Perhaps you can suggest a better resource.
Thanks again,
Sean.
Lindsay, Ontario.
 
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