Vintage Outboard Carburetor Basic Maintenance for Johnson / Evinrude / OMC

Your vintage outboard motor can run for decades with easy to learn maintenance practices. This video provides a basic overview of a vintage carburetor off of a 1956 12HP Johnson / Evinrude / OMC engine. This carburetor design was re-used over a period of many years with minor differences from year to year.
Step 1: remove choke knob and mixture knobs.
Step 2: remove motor cover
Step 3: disconnect throttle linkage from carburetor (tiny cotter pin or bent wire)
Step 4: remove 2 nuts (7/16") holding carburetor onto intake manifold
Step 5: carburetor can be completely separated from engine
Step 6: turn carburetor upside down and remove 4 or 5 screws with a screwdriver
Step 7: remove float hinge pin by pushing one side of it with a small pointed tool
Step 8: remove float and needle valve
Step 9: remove gasket
Step 10: remove low speed mixture screw, packing nut and washers (the washers are probably inside the hole!)
Step 11: remove high speed mixture screw, packing nut and washers
Step 12: remove high speed carburetor jet with screw driver
Step 13: clean all parts and replace gaskets, float, needle valve as needed
Step 14: reassemble in reverse order
Step 15: before attempting to start the engine, pre-set the high speed and low speed mixture screw needle valves as follows:
High speed screw: A beginning "rough" adjustment for the
high-speed needle valve is 3/4 of a turn out
(counterclockwise) from the lightly seated
(closed) position.
Low speed screw: A beginning "rough" adjustment for the low-speed needle valve is from 1 to 1+1/2 of a turn out (counterclockwise from the lightly seated (closed) position.
Carburetor Tuning will be covered in a different session.

[@mannurse1978]

Man I just want to say thank you rebuilding a 1956 30 horsepower Evinrude and your help is awesome....

[@robertwarner7231]

Perfect. With the low an high speed setting just what i was looking for on how to do..

[@highlandoutboards]

So happy to hear the positive feedback. Keep those antique outboards running!

[@hotrodZack1948]

oh my god im new to boats and i just got a 58 johnson super seahorse. and it has been driving me nuts trying to get it to run. so i took the float bowl down to see if it was getting gas because it would start on carb cleaner spray but not with choke ect. i could see gas in the fuel filter ect. the float needle was "upgraded" at some point and had a rubber tip that is now swelling i assume with modern fuels. so anyway i got that unstuck but it did it again today but it wasnt running very well and i noticed that 2 o rings were laying in the bottom of the bowl when i took it off. i had no idea what they went to, and now i know what they were thanks to you haha. someone replaced that gasket on the bottom of the jet/bowl with 2 rubber o rings.... DOH! im ordering a carb kit now.

[@outboardfixer]

Good info

[@kodibassInsideoutboards]

Great vid, I agree very basic carb,, that will last & last

[@highlandoutboards]

Thanks! Will make a more advanced rebuild video soon.

[@JayHughart]

Thanks for your reply. Already pulled the Welch plug and it was super clean inside. Im thinking the old cork float is not properly buoyant and ordered a new one. I have done the link sync cam mark to throttle lever and it helped a little but it should idle with lower throttle than the cam mark. Runs great other than that but even properly (as in best settings) for the knobs the exhaust is eye burning rich.

[@Boscovius]

Did you try adjusting the low speed idle screw? It sits just behind your throttle linkage. It's supposed to be used to set the lowest idle point. I know this post is four years old, but just putting this out there. 1957 Big Twin 35.

[@rustybennett825]

I have a 1947 Elgin 3 1/2 hp the carb was in pieces all there how can a get carb diagram for itt

[@highlandoutboards]

John Dunn, my first suspicion is that your carburetor is not getting complete fuel flow from the float valve. Have you checked your needle valve and float assembly?

[@aguistud1]

Hi, question on the needles... What are the best "washers/Orings" to use on the packing nuts? and should Teflon tape or thread paste be used on the needles and or packing nuts?... I am re-installing the needles on an old 50s outboard with the same carburetor as the one you are showing, thanks

[@highlandoutboards]

The valve packing washers I use are available through boats.net I usually install 2 of these in each valve, and no need for Teflon tape. Part Number is 0307583.

[@rachelgarwood5809]

ivbi

[@shawnnelson2920]

Im currently working on my 1966 Johnson 9.5...took it out the other day and she trolled nice for about 20 minutes...then went to turn the boat around and gave some more throttle and she was bogging down ..finally she stalled and i could not get it to start back up. I took the inlet to the fuel pump off and the screen had some gunk and debris on it..bought a new gasket and screen , replaced them today. I also added an inline fuel filter to the gas line from the tank to the outboard. Is there anything else i should check? Thanks for your great informative videos ! Shawn

[@highlandoutboards]

Shawn Nelson If your outboard is running fine after clearing the debris, I'd leave it alone. If you still have trouble, the debris may have also affected small passage ways in the carburetor. That's the next place to troubleshoot based on what you've written.

[@shawnnelson2920]

highlandoutboards well i got it to run awesome at trolling speeds..--but i noticed when i go full throttle the motor vibrates and closes the choke, she sputters then dies if i dont catch it quick enough. I also noticed theres 2 bolts on the lower cowl mising and they look like they go to the dampener ...i looked online for the bolts..but not sure if im looking at the right ones.. I just need to know the thread size and length of the bolts..im hoping if i can get bolts for it, it wont shake so much that the choke closes...

[@marklindroth1163]

Can I put a 6 hp carb on a 4 hp motor

[@JayHughart]

I have a 1955 evinrude 15hp had the carb off a dozen times. It simply will not idle it will run down to the mark on the throttle cam and stalls anywhere below that. New points and condensers. Any help is much appreciated its driving me nuts!.

[@highlandoutboards]

Around the 45-50 second marks in the video, you can see a bright circular aluminum feature on the top of the carburetor. This is called a welch plug. A complete carburetor rebuild and cleaning would include removal of the welch plug and cleaning out of the chamber it covers. My suspicion is that you have debris or something clogging the very small low speed fuel circuit under this plug. You will need to get a carb rebuild kit for your carburetor model which includes replacement welch plugs. These are not reuseable. You will have to use a nail or a screw or an icepick or something to get your old one out. Clean the low speed chamber underneath it really good, then put a new welch plug over the top and hit it sharply one time with a punch to press it into place.

[@larrybarclay2422]

Did you replace the packing rings under the packing nut? If air is going past the needle valve , engine will never run right

[@scotthofmann7097]

do you have a video on how to rebuild the carbs for 85 HP evenrude 1987

[@highlandoutboards]

***** We only work on pull-start outboards -- nothing as big as yours.

[@easttnout]

I have a 1957 10hp johnson i got from a friend who didnt need it anymore it had set in his barn for 3 yrs . I had another friend take a look at it and everything worked. He cleaned it up and rebuilt the carb . I brought it home and adjusted the carb and the motor will run very well but then if you come back the next time it wont run on the settings you set it at next time and you have to start all over with adjusting it anything you could tell me that would help ? Sorry this was so long

[@highlandoutboards]

EastTnOutdoors I'd like to hear a little more about the symptoms. If you get the motor running well then stop the motor, will it start right back up and run just as well? How long does the motor sit between outings where the carb adjustments have to be re-done? Do you disconnect the fuel line and run the outboard dry before putting it away at the end of a trip? Does the motor sort of "cough" when you start it cold after with the mixture settings that worked well the last time you were out? Without these answers, my first guess is that the settings you use when the engine is warm to get the motor to run like you want it to may be too "lean" -- I recommend getting the carb settings to where you get the best rpm's and the best sound, then go a little richer (counter clockwise) until you just start to hear the engine performance change. Be sure to wait about 15 seconds between adjustments to let the mixture setting stabilize.

[@easttnout]

It will run great you can shut it off and start it right back up . The "cough" you mentioned does happen often but a little adjustment and it stops sputtering . It usually wont restart after say 12 hrs. or so of being started also when I go to start it say the next day the clear bowl under the carburetor will be almost a brown then I get it started and it will go back to the mixed gas color in the bowl. I do not usually disconnect the fuel line connector after I have attempted to set the carb . I had set it set beautifully in the barrel got it out on the boat for the first time and the darn thing wouldn't even start so I had to spend 5 plus minutes adjusting it to even get it running and then it ran awful so I didn't keep her out long brought it home got on Google and now im here . Sorry if that's not much help im not a engine guy per say that's why I need help lol

[@highlandoutboards]

Is there a chance you are using old gas or could there be traces of water in your gas tank? One of our customers had similar problems that were addressed with a fresh tank of gas. Also, on a cold engine you might see if choking for one pull only helps. Use half choke for the next couple of pulls and then no choke.

[@easttnout]

tank was empty when I got it and that's usually how I start it using the choke the way you described

[@wimd101]

bedankt,

[@highlandoutboards]

graag gedaan

[@leomatos1980]

Hey buddy. I have a.problem with my 69 johnson outboard, and the problem is.that have o pull the second flap throttle all the way to start, but after it turn on, I release it and it dies immediately, what can I do?

[@highlandoutboards]

sounds like the low speed fuel supply is blocked. this could be because the carburetor is dirty or because the low speed mixture screw is set too lean. Twist the top adjustment needle clockwise gently until it just reaches the bottom (lightly seated), then untwist the needle counterclockwise one full turn. Try that, and if it doesnt improve, carb probably needs a thorough cleaning.

[@mattbranum5847]

what do you set the high speed and low speed adjustment knobs too for starting? I have a 57 15hp evinrude aquasonic.

[@highlandoutboards]

The starting position for the low speed mixture screw is 1 to 1.5 turns counter-clockwise from a lightly seated position. The starting position for the high speed mixture screw is 0.75 to 1 turn counter clockwise from a lightly seated position.

[@mattbranum5847]

Much thanks for your response and the information. I got it running today!

[@highlandoutboards]

+Matt Branum You're welcome! Glad to hear it's running.

[@dalemoffett6891]

hi, I have a '58 Johnson seahorse 18. the slow speed adjustment needle on the carb is sort of in free spin, i can't get it out to clean it is this normal or do I need a new carb?

[@jamesbisett496]

That's unusual. It's possible that the gaskets are holding the needle inside the hole. I'd give it a good solid pull and see if you can get it to release.

[@mumbles552]

It's been a few years but did you ever get the needle out? It threads thru an aluminum sleeve which slides into the carb housing. After cleaning all, of the old packing washer material out, it should slide right out. A bit of heat may help.

[@johndunn8429]

I've been working on a 1953 Johnson 15hp outboard, and I just can figure the carburetor adjustment out. I've done the 1.5 turn on the fuel screw an the 3/4 of a turn on the speed screw and I can't figure it out. Engine starts and runs for 2 seconds lol

[@gerardjones7881]

keep it running with the choke until it warms up.

[@DOwhutnow]

Hope you still have it. I also had problems with it. My pressure table had a leak in the old lines and then in the bagel assembly on the tank

[@JayHughart]

Oh and no matter what it seams to be running rich. exhaust burns my eyes. Strange the needles both seam to be adjusting it and it will lean out and sputter/kickback when adjusted too lean.