Johnson 150 carb rebuild

[Ky86cajun]

I have a 1985 Johnson 150 that I’m gonna rebuild the carbs on, I was wondering do you guys do a basic needle and seat, gaskets and float rebuild or do you tear them completely down and replace every o ring etc? The kits I bought have several o rings that the videos I’ve watched doesn’t cover on where they are and how to get to them. I’ve rebuilt several car carbs and engines, but this is my first attempt at a boat carb and can’t seem to find any in depth videos on a complete tear down if that’s what’s needed.

[omcforever]

An OMC service and repair is your friend.(not Clymer or Seloc) When doing them, follow the procedures in chapter 2. The complete kits(only use OMC/BRP parts) cover a few models so there may be a few parts you wont use. Dont do a partial but a complete job and if you follow the book, you should have no issues.

[omcforever]

And dont be tempted to soak in carb cleaner especially overnite. Emulsion/transfer and idle tubes are installed with a special adhesive and will be damaged if you do that and create all kinds of runability issues. Crossflows use rubber o-rings on the bowl drain screws(2 per carb) and 1 to retain the throttle roller on the middle carb..Follow the book. Some of the YouTube videos will get you into trouble. Good luck.

[omcforever]

https://www.boats.net/catalog/evinru...cos/carburetor

[omcforever]

One other thing is insure float chamber mating surfaces are flat. Place a piece of 180-240 grit sand paper on a plane of glass and sand in a circular motion until no low or high spots are present and torque them to spec(24-36 inch pounds) in 4 increments using OMC Screw Loc or equivalent on screws in a chris cross pattern. When taking carbs off, dont loosen any linkage screws/dont loosen middle carb pickup roller. All you need to do is un-clip the long bar that connects all three/each end just snaps out. When you get it back together, all linkage should be close to the way it was before taking them off.(assuming they are correct before hand) Also insure the middle card throttle roller/cam follower is present. Item 23 in the above parts diagram. I would perform a link and sync afterwards just to be sure all adjustments are right. 2 strokes are un-forgiving/damage could occur if not right, unlike a car or truck 4 stroke. Just curious, are you chasing a problem?

[Ky86cajun]

Thanks for the information, and yes I’m chasing a problem or three lol. First it wants to die at idle after it’s been ran for awhile....two, I was running wot at the lake a couple weeks ago and it just died like the fuel was shut off.....and I have a couple cylinders running a little lean and a couple running rich. The guy I bought it from said he found it from someone who had it sitting for a few years. He said he thought it wasn’t getting enough fuel so he installed an in-line electric fuel pump(which I’m going to take off) I want to make sure the carbs are clean and running right to eliminate those from the equation.

[omcforever]

) I want to make sure the carbs are clean and running right to eliminate those from the equation.

Heading in the right direction. Lean is a killer of 2 strokes,,,quick. Do a compression check and post up the results. Also, while the carbs are off, check/clean/service or replace the re circulation check valves in the intake per your OMC service manual. Check valves are item 7 in the attached below diagram. OMC part #0392988 (6 of them/little brass fittings with rubber tubing on them). Inspect all rubber hoses good especially being old and sitting and use proper hose clamps under the hood(black nylon/not just regular tie straps) OMC part #0320107. replace if needed and replace all fuel filters. Dont want to suck crap back into fresh carbs.

https://www.boats.net/catalog/johnso...ntake-manifold

[omcforever]

And if gas in tanks is more than a few weeks old, get rid of it and replace with 89 octane. Get rid of that electric pump and re-install original type VRO or a MaxRules stacked pulse pump set up and mix fuel-oil 50:1.

https://maxrules.com/VRO_06-200.php

[Ky86cajun]

It still has the working vro, that’s why I don’t get why he installed an electric fuel pump. I’ve already done a compression check beforehand and they all were between 85 and 92.

[omcforever]

Also, when carbs are apart, remove main-mid-idle orifices and clean passages and verify sizes with carb diagram. Also remove carb core Welch plugs and clean cavity and passages and reinstall new plugs. Also post up model number of motor so as we know exactly what we are dealing with,,,

https://www.boats.net/catalog/johnso...cos/carburetor

[omcforever]

It still has the working vro, that’s why I don’t get why he installed an electric fuel pump.

Probably trying to band aid a problem/lack of knowledge.

[omcforever]

If you are not comfortable doing the carbs,,send them to me and I will go thru em for you. Just cover postage and include the kits.

[Ky86cajun]

I can’t find the model number of the engine, the numbers are wore off where they are usually at on the tilt and trim. I do know it’s a 1985 Johnson 150GT

[omcforever]

If your flywheel is like the black one then it is a GT150. If it is like the silver/aluminium one then it is a standard 150...

[Ky86cajun]

It’s the black one....what’s the difference between the GT and standard?

[omcforever]

GT150 has a 35 amp charging system, bigger bore carbs/different jetting, higher compression heads, special venting on engine cover.

[Ky86cajun]

Oh ok I was wondering....figured it was something “extra”

[omcforever]

Stout motors when running right...

[Ky86cajun]

So can I use carb cleaner to shoot through passages and not mess up the adhesive or should I just use compressed air?

[omcforever]

Carb spray cleaner and I follow up with brake clean to clear away any residue and also the brake clean has good pressure and cleans out passages as well.