Carburettor Confusion

[meomia]

Hi,
I have just bought a Johnson 20R71S motor. I do not know its history and I know nothing about outboards.

It starts but will not idle. Checking carburettor info it seems the carb on this motor is different to the standard 20hp carb.


Can anyone tell me what model this carb is from and how I can tune it? There is a rich / lean adjustment plus a fast / slow knob.

 

[nwcove]

Re: Carburettor Confusion

Carb looks standard for that motor. probably just need a good cleaning ( top secret file at the top of this forum), and a re-kit.
Johnson Carburetor Parts for 1971 20hp 20R71S Outboard Motor

 

[HighTrim]

Re: Carburettor Confusion

Pull it off and take it right apart. Soak it in your wife's Pine Sol overnight. Then wash it off in hot soapy water, and blow with compressed air. May want to shoot some Parts Cleaner or Carb cleaner through all the passages as well, then blow with compressed air again. Now time to rebuild. There is a thread in the FAQs about this.

As far as tuning, there is also a thread by Joe Reeves on how to do it. The top needle is the slow speed needle, the bottom the high. The low's initial setting is 1.5 turns out from lightly seated, the high is 3/4 turn out from lightly seated. Then tune from there on the water.

 

[nwcove]

Re: Carburettor Confusion

Pull it off and take it right apart. Soak it in your wife's Pine Sol overnight. Then wash it off in hot soapy water, and blow with compressed air. May want to shoot some Parts Cleaner or Carb cleaner through all the passages as well, then blow with compressed air again. Now time to rebuild. There is a thread in the FAQs about this.

As far as tuning, there is also a thread by Joe Reeves on how to do it. The top needle is the slow speed needle, the bottom the high. The low's initial setting is 1.5 turns out from lightly seated, the high is 3/4 turn out from lightly seated. Then tune from there on the water.

maybe im looking at the exploded view wrong, but it sure looks like that motor has a "fixed" hs carb jet.????

 

[HighTrim]

Re: Carburettor Confusion

Yeah according to marineengine it has a fixed high speed jet. In his pic#1 though looks like a needle and packing nut in its place. I assumed that the dial was a multi function dial where there are actually 2 dials in 1. Perhaps I was wrong? I was just going on his pics, didnt check the manual.

 

[HighTrim]

Re: Carburettor Confusion

I had thought that was maybe what he meant by his being different from the standard as he stated. Perhaps some fitted a adjustable needle in its place.

 

[seahorse5]

Re: Carburettor Confusion

The model number is for a 1971 but the carb looks like the old style, prior to 1968 or so.

Is the power head painted white color? If so, it is probably a 1966 or earlier block as1967 was a light green.

 

[boobie]

Re: Carburettor Confusion

Agree, the carb doesn't look std for the model # given and the pics.

 

[meomia]

Re: Carburettor Confusion

Just to clarify my confusion:

The parts breakdown I have seen for the 20R71S motor only has one adjusting knob which operates the top shaft/needle valve. These parts lists specify "for motors sold in USA". Mine was originally sold in Australia so perhaps a different model or different parts fitted.


My motor has an inner knob with a shaft into bottom of carby. The outer adjustment works top shaft. The label says rich <> lean and underneath Slow Speed. The "powerhead" that is the motor itself, is painted white.

I was not sure which adjustment is the slow speed and which is the mixture.

There appears to have been some packing on the lower shaft. Should there be a leather seal or "O" ring here?

What is the correct fuel / oil mix? I am currently using 50:1 gas to oil. Is this OK.

When running there is some smoke. Not sure if this means mixture is too rich or too much oil in mix.


Thanks in advance for all the help.

 

[meomia]

Re: Carburettor Confusion

Pull it off and take it right apart. Soak it in your wife's Pine Sol overnight. Then wash it off in hot soapy water, and blow with compressed air. May want to shoot some Parts Cleaner or Carb cleaner through all the passages as well, then blow with compressed air again. Now time to rebuild. There is a thread in the FAQs about this.

As far as tuning, there is also a thread by Joe Reeves on how to do it. The top needle is the slow speed needle, the bottom the high. The low's initial setting is 1.5 turns out from lightly seated, the high is 3/4 turn out from lightly seated. Then tune from there on the water.

I would like to know what the carb is from before I try to purchase a kit. If the 20R71S carb has a fixed bottom jet would would the kit have all the parts needed for my carb?

Also I am hesitating on pulling it apart in case I damage something and then cannot get part.

I have re-set the needle valves to 1 1/2 turns and 3/4 turn and it does run better once warm. Still rough idle though.

 

[HighTrim]

Re: Carburettor Confusion

50:1 is ok.

I was assuming it was a multi dial. The dial that turns the bottom needle is the high speed adjustment. The dial that turns the top needle is the low speed adjustment. The more you turn them to the right, or clockwise you are leaning the air/fuel mix at either high or low speed operation depending on what needle you are turning. Same for both turning the left or CCW, you are richening the air/fuel mix.

The carb kit will be fine. All the internals are still the same.

Have a read in the FAQs, it should help.

If you are running in a barrel, she is going to smoke no matter where it is set. That is normal.

 

[seahorse5]

Re: Carburettor Confusion

Is the power head painted an off-white color? It looks that way in the second picture that you posted and if so, it is older than a 1971 engine.

 

[lindy46]

Re: Carburettor Confusion

Get a kit and clean/rebuild the carb. Make sure to remove that little welsh plug you see at the top rear of the carb. That is the idle circuit and there are small holes under there that get clogged up and cause idle problems. Use a thin wire to clean them out then spray with aerosol carb cleaner. You can roughly adjust the idle in a test tank, but final adjustments will have to be made in the water. Once you get the high speed adjusted to optimum (adjust at WOT) you shouldn't have to touch that one again. Then adjust the low speed for optimum idle/trolling.