AAAGHH! '57 18hp carb--won't get fixed!

[jbjennings]

I have an 18hp johnson-'57 model. I've rebuilt the lower unit and carb but it still is having the same HORRIBLE lean cough as it did before rebuilding it. I know it's the carb cause I used the one off my other 18hp and it ran fine. It runs good higher speed but not on idle at all without coughing really bad. I tried putting the low speed needle from my other carb in it but same result. I feel like I cleaned it really well. Any idea of what might be wrong? Turning the low speed needle valve has no effect whatsoever. I thought the needle valves control fuel flow--am I right? What controls the air flow on low speed? Is there a passage that is clogged that I obviously missed? This darned thing has me baffled... Thanks to your help I am getting the hang of resealing lower units and fixing water flow problems but still have had only a couple of successful carburetor fixes on my old OMC's.
Thanks,
JBJ

 

[wbeaton]

Re: AAAGHH! '57 18hp carb--won't get fixed!

Turning the low speed needle valve has no effect whatsoever

Its not clean. Did you pop the welsh plug off that sits above the low speed needle? There are some holes in there that make up the idle and intermediate fuel flow circuit. They needed to be clean or you won't idle properly. Also, clean out the old packing and reseat the low jet with new packing washers. I also like to use a little silicone on the welsh plug edges to ensure there is no loss of vacuum.

 

[jbjennings]

Re: AAAGHH! '57 18hp carb--won't get fixed!

WBeaton,
Yeah, I took out the Welsh plug but didn't seal it with silicone--I'll try that. I did take it out, check those little holes and everything looked fine. I also looked through the needle valve orifice and it looked spotless. I put a new carb kit on it so new packing, etc. I'll take it apart again and see if I can locate a stopped up passage. By the way, I figured out how to post pics--maybe I'll get a few bites on my other thread--hope you'll post some--got any of yours running?
Thanks for the help,
JBJ

 

[wbeaton]

Re: AAAGHH! '57 18hp carb--won't get fixed!

It sounds like something is still dirty or the low speed needle isn't seating properly. Did you clean out the old packing as well?

Most of my motors run. Some run, but still need some attention. Isn't that always the way? lol I didn't notice the other thread you are talking about, but I'll take a look for it.

 

[jbjennings]

Re: AAAGHH! '57 18hp carb--won't get fixed!

WBeaton,
Yeah, I did clean out the old packing but something must still be in there like you said. BTW, I want to see a pic of that evin. 18, '51 evin. 25hp, and your evin. 15 running--I liked 'em. As you can see from my posts, I'm still working on getting mine "right", too. I'm going to see if I can get some sleeves or something done about my grooved shaft and 9.8 merc prop shaft--will let 'ya know how that works out in case you have any like that. Also, I looked at a brand new 2008 merc 25 4-stroke and they were crazy enough to put the weight on the sticker--would you believe they said it weighed 157 lbs.? I'm thinking that '55 evin. 25hp I have on the way is a "featherweight" compared to that thing. I'm really suprised that people are liking the 4-strokes so well, they're too heavy and feel too wimpy to me even though they are cleaner and get better fuel mpg on the average. Will let you know how the carb comes out.
Thanks,
JBJ

 

[BoatBuoy]

Re: AAAGHH! '57 18hp carb--won't get fixed!

If you haven't already, get an aerosol can of Super-Tech carb cleaner from Wal-Mart, or equivalent, that has a straw (about $1.25). Put that straw up into each orifice/passage and blast away. Sometimes stuff needs to be blown out and that carb cleaner will clean the black off a Halloween cat.

 

[rick48cj2a]

Re: AAAGHH! '57 18hp carb--won't get fixed!

Good plan but make sure to wear eye protection. If the passage is plugged it can blow right back into your face. That stuff will remove just about anything.

 

[jbjennings]

Re: AAAGHH! '57 18hp carb--won't get fixed!

SHE"S FIXED!!!! A passage running up the side of the bowl was stopped up TIGHT! I guess I forgot to pay attn. to that bowl 'cause I figured it was the low speed jet. Thanks to your suggestions and my new $7 telescoping air blower and about 100lbs. of pressure, I found it. I should have immedialtely saw it with the carb cleaner but you have to be smart enough to try it to find it stopped up. Larsen (my son) and I are going to test it today and see if our l.u. seal job worked, too. We'll bring the GPS and see how fast she'll run and post it on WBeaton's "How quick does your outboard push" thread.
Thanks men,
It was sure satisfying to finally fix that rascal!
JBJ

 

[wbeaton]

Re: AAAGHH! '57 18hp carb--won't get fixed!

Good for you! That is a great lesson why you should always blow out all the passages with compressed air. Its just so easy to miss a "gob of gunk".