Johnson 30hp running very rich after carb rebuild

[mixin]

Re: Johnson 30hp running very rich after carb rebuild

quick question about these carbs....
the small inlet nozzle that sits inside the larger tube that the float surrounds. is it supposed to be perfectly in the center within that tube? mine is at an angle and the end of the inlet nozzle touches the edge of the outer tube. '85 30hp seahorse.

yes, mine is at an angle also. Welcome aboard! FYI, if you have questions of your own please start a new thread - thanks.

 

[mixin]

Re: Johnson 30hp running very rich after carb rebuild

I was having a problem just like this with my 40hp. Would not adjust with the idle screw would only run at 1200-1400 rpm no lower. Found 1 reed was sticking open just a hair. Took it off and massaged it back a little bit and solved the problem. I would bet that is the issue.

Thanks, I will keep that in mind! The only thing that makes me think carb is that the engine did not run this way before I "fixed" the carb by rebuilding it!

 

[mixin]

Re: Johnson 30hp running very rich after carb rebuild

proper sparkplugs and gap?...float is positioned with the tab on the metal arm pointing upward towards the carb body?...link%sync ok?

Plugs were new last fall, I will check them to make sure they are the proper model and gap. The float has a notch cast into it, I think I remember making sure it matched the picture in the factory service manual when installing it so I would not install it upside down. I think I know what link and sync is - something to do with spark timing vs. throttle position? I have no idea on that one - I've never checked it on this or any other engine.

 

[AlTn]

Re: Johnson 30hp running very rich after carb rebuild

the "tab" I refer to is on the metal adjustment arm where the float hinge pin goes through...just my mantra "tab up" as I'm more than capable of putting the float on upside down...link%sync is as you've stated....the cam roller should center on the timing mark on the timing cam when the throttle is in the start position..at this position the throttle plate should just begin to open....at WOT the roller should be on the highest point on the timing cam and the throttle plate will be horizontal in the carb throat

 

[Cofe]

Re: Johnson 30hp running very rich after carb rebuild

After rereading this thread, my thoughts are that there is something wrong with the low speed fuel circuit in the carb. The low speed needle should change motor response. If it were me, I would remove the plastic carb top, remove the low speed mix needle, and spray carb cleaner into the needle passage and in the passages visible on the carb body. Find a strand of copper electric wire to use to poke the passage ways on the carb body. Visually inspect the plastic top and clean any passages in it. Also make sure the gasket is just like the one you removed. I just fixed a similuar situation with a Nissan motor, and found a small passage was blocked.

 

[mixin]

Re: Johnson 30hp running very rich after carb rebuild

After rereading this thread, my thoughts are that there is something wrong with the low speed fuel circuit in the carb. The low speed needle should change motor response. If it were me, I would remove the plastic carb top, remove the low speed mix needle, and spray carb cleaner into the needle passage and in the passages visible on the carb body. Find a strand of copper electric wire to use to poke the passage ways on the carb body. Visually inspect the plastic top and clean any passages in it. Also make sure the gasket is just like the one you removed. I just fixed a similuar situation with a Nissan motor, and found a small passage was blocked.

Thanks for the reply. I was going to ask if I could do this while the carb is still on the engine (because it's so fun to take the starter on and off!), but I think that might be a bad idea. I really won't have any time to fix it until we go camping at the lake this weekend (when I was hoping to have the boat running). This whole thing is bothering me so much that I think I'll end up tearing the carb down again on the picnic table at the campsite! I just wont have any shop air - which sucks. There are a couple of welch plugs I did not mess with that I'm going to take out and clean behind and I will check over my previous work as well.

As for the float setting, I have a measurement for the drop in the manual (mine was in spec). I do not have the float height checking tool - is there another way to make sure that the float rise is set ok? In a response above on this thread, I think someone said "with the carb inverted the float body should parallel to the carb body where the lower float bowl attaches (that's how mine is set now). Does this sound ok? Thanks.

If all else fails, watch for me - I'll be the guy the 40lb bow mount and 50lb transom mount trolling motors cruising around with a 30hp paperweight on my stern!

Thanks for the help everybody! Out of respect (and duty) to the community here, I will make sure to post here until this problem is resolved to properly close out this thread.

Mike

 

[mixin]

Re: Johnson 30hp running very rich after carb rebuild

After rereading this thread, my thoughts are that there is something wrong with the low speed fuel circuit in the carb. The low speed needle should change motor response. If it were me, I would remove the plastic carb top, remove the low speed mix needle, and spray carb cleaner into the needle passage and in the passages visible on the carb body. Find a strand of copper electric wire to use to poke the passage ways on the carb body. Visually inspect the plastic top and clean any passages in it. Also make sure the gasket is just like the one you removed. I just fixed a similuar situation with a Nissan motor, and found a small passage was blocked.

I couldn't get this quoted response out of my head while trying to think about what went wrong with this carb rebuild. It has to be something with the low speed circuit...well it was. In my haste to get the carb back together (getting dark, kids needing to get to bed), I installed the gasket beneath the plastic top on the carb backwards. No wonder why adjusting the low speed screw did not change anything - it was totally blocked off by the gasket! Glad I checked that before taking the carb all the way off again!

After that, the motor seemed to run better and once I set the low speed screw to 1.5 turns out (as directed by contributors to this post, instead of 2.5 turns out as per factory service manual) the engine would now finally idle with the throttle control up and centered. Hopefully, all that's left to do now is fine tune the low speed screw with the boat in the water.

Sorry to drag everyone through this for my bonehead mistake. I am very grateful for the help, I really learned a lot from all who responded. Thanks again so much!

Mike

 

[fireman57]

Re: Johnson 30hp running very rich after carb rebuild

It's always nice to find the problem yourself. Makes you feel good. Have fun on the camping trip. If nothing worse, you have idle speed which beats a trolling motor! Keep up posted

 

[oldrudedude]

Re: Johnson 30hp running very rich after carb rebuild

as above. We all learn....... thanks for that experience.