Carb Adjustment? '72 Johnson 85HP

ADK_Boater

Petty Officer 1st Class
Joined
Jun 29, 2010
Messages
217
Does anybody know how to properly adjust the carbs on this year 85HP? Or have any insight into what to do for the following problem.
What I mean is that in '72 they did away with the low idle adjustment screws (in '71 there were two per carb), The passageways where the screws were are still there but in '72 they plugged up the holes with small bolts and gaskets (otherwise an identical carb). I checked many schematics for '71, '72, '73 etc.
I just can't seem to get fuel to the cylinders properly. I've been trying to solve this problem for some time, so I've cleaned and tuned the carbs to spec, taken apart cleaned and reassembled the fuel pump (new), reed valves (look great), fuel lines (clear and open), everything from the gas tank to cylinders and everything in between.
I have plenty of spark on all 4 cylinders.
Good compression between 115-120 on all 4 cylinders.
I've even had my starter rebuilt by professionals.
What I have noticed is that when I pull the spark plugs after cranking it over for while there is no real smell of gas in the combustion chambers. I've checked them all. I've lubed the cylinders from time to time with pre-mix in a squirt bottle so as not to damage the cylinder walls or piston rings. But that is the only time that they smell like gas.
So from months of trial and error, I have narrowed the problem down to two possibilities.

1. I have poor primary compression in my crankcase (I've got a new gasket on order but there was not a problem that could be seen on the original one).
2. I haven't...or can't adjust the carbs properly enough so that the fuel/air mixture flows into the combustion chamber. I think this possibility is more likely.
What the heck should I do?

If you have any info, knowledge or thoughts, they,would be appreciated.
ADK.

P.S. I forgot over the winter why I love boats so much...now I remember.
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: Carb Adjustment? '72 Johnson 85HP

Did you manually clean the 2 "Idle" and 2 "High Speed" jets in each carburetor with a piece of single strand steel wire, then blow them out with compressed air? If not do so as solvent just doesn't do the job properly.

The above is normally the cause of the problem you describe.

The carburetors can only be adjusted by changing the size of the jets. If the engine ever ran normally, the jets are the proper size in which case... DO NOT change them!
 

ADK_Boater

Petty Officer 1st Class
Joined
Jun 29, 2010
Messages
217
Re: Carb Adjustment? '72 Johnson 85HP

Thanks Joe,
I will definitely clean the carbs in the method you described.
However I am not sure if the engine ever ran properly since I've only had for a year and a half. In that time I have never been able to start it.
I'll keep at it until it roars to life!
I'll update you all as well when I make some progress.
Thanks again!

ADK
 

ADK_Boater

Petty Officer 1st Class
Joined
Jun 29, 2010
Messages
217
Re: Carb Adjustment? '72 Johnson 85HP

Hey everybody,

Can anybody explain the idea behind the removal of the low idle needle/screws for the '72 carb?
Since they plugged up the passageways with bolts that year, and the carb is otherwise the same, then what was the reasoning for that in the first place?
Was that year notorious for not starting properly, or not supplying sufficient fuel?

I have not had time after work to put everything back together, but I'm wondering about getting the proper air flow through the carb so that a sufficient amount of premix gets to the crankcase and cylinders.

Any thoughts, ideas, answers or knowledge would help.
Thanks again!

ADK
 

jquinn13

Recruit
Joined
Jun 11, 2011
Messages
5
Re: Carb Adjustment? '72 Johnson 85HP

I'm having the same problem! Are we supposed to tighten the high speed jets all the way? Or 1 1/2 turns? [1 1/2 turns would be for the needle valves that they got rid of] . I changed my engine coil, all new wiring harness, new electrical components, so I rebuilt the carbs myself and probably didn't put them back together correctly. I'm glad we are having same issue. So, It is more than likely the carbs adjustment. Anyone please reply with instructions. Checked my linkage again same issue. How much do you turn the slow idle screw?

JQ


Does anybody know how to properly adjust the carbs on this year 85HP? Or have any insight into what to do for the following problem.
What I mean is that in '72 they did away with the low idle adjustment screws (in '71 there were two per carb), The passageways where the screws were are still there but in '72 they plugged up the holes with small bolts and gaskets (otherwise an identical carb). I checked many schematics for '71, '72, '73 etc.
I just can't seem to get fuel to the cylinders properly. I've been trying to solve this problem for some time, so I've cleaned and tuned the carbs to spec, taken apart cleaned and reassembled the fuel pump (new), reed valves (look great), fuel lines (clear and open), everything from the gas tank to cylinders and everything in between.
I have plenty of spark on all 4 cylinders.
Good compression between 115-120 on all 4 cylinders.
I've even had my starter rebuilt by professionals.
What I have noticed is that when I pull the spark plugs after cranking it over for while there is no real smell of gas in the combustion chambers. I've checked them all. I've lubed the cylinders from time to time with pre-mix in a squirt bottle so as not to damage the cylinder walls or piston rings. But that is the only time that they smell like gas.
So from months of trial and error, I have narrowed the problem down to two possibilities.

1. I have poor primary compression in my crankcase (I've got a new gasket on order but there was not a problem that could be seen on the original one).
2. I haven't...or can't adjust the carbs properly enough so that the fuel/air mixture flows into the combustion chamber. I think this possibility is more likely.
What the heck should I do?

If you have any info, knowledge or thoughts, they,would be appreciated.
ADK.

P.S. I forgot over the winter why I love boats so much...now I remember.
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: Carb Adjustment? '72 Johnson 85HP

I'm having the same problem! Are we supposed to tighten the high speed jets all the way? Or 1 1/2 turns? [1 1/2 turns would be for the needle valves that they got rid of] . I changed my engine coil, all new wiring harness, new electrical components, so I rebuilt the carbs myself and probably didn't put them back together correctly. I'm glad we are having same issue. So, It is more than likely the carbs adjustment. Anyone please reply with instructions. Checked my linkage again same issue. How much do you turn the slow idle screw? JQ

Fixed brass jets are not adjustable. They must be seated so tighten them... all of them.

And your engine is what? If also a 1972 85hp, both the idle and high speed mixture (fuel/air) are fixed brass jets and are not adjustable.
 

ADK_Boater

Petty Officer 1st Class
Joined
Jun 29, 2010
Messages
217
Re: Carb Adjustment? '72 Johnson 85HP

Thanks Joe, I'll make sure they are tight.

I'm gonna invest in a new battery too. The one I have is leaking acid slightly out the top...I know this because my pants have little faded holes in them now:facepalm: LOL

I think the battery may have been week...it's older...not sure but since it is leaking acid it's a good excuse to get a new one.
 
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