How hard is a carb rebuild?

[superbenk]

I've finally gotten to the point where I think I need to rebuild the carb on my 30 yr old boat. It's a 1980 Century 190 w/ an OMC 140/400 outdrive with a Rochester 2GC 2bbl carb. I've pulled the carb off & opened it up, cleaned it thoroughly, etc. I have the rebuild kit too.

I'm just wondering how hard it is to rebuild a carb for someone who is very much an amateur with engine repair? I've done plenty of light engine repair & tuning, but I've never dug into a carb or rebuilt an engine or anything like that. The instructions seem fairly straight-forward, but am I getting in over my head?

If I do go ahead with the rebuild myself, what kind of adjustments will I need to do (assuming I don't change any of the linkages/current adjustments, etc)? Are there special tools I should have? Are there any tips/hints I should know prior to starting the rebuild?

 

[ziggy]

Re: How hard is a carb rebuild?

i don't know the specs on your omc set up. but you'll be able to find them in a omc service manual i'm sure. use that for your specs.

the 2gc is a easy carb to rebuild. not many parts as carbs go.

I've pulled the carb off & opened it up, cleaned it thoroughly, etc.

does that mean ya've taken it totally apart? down to the last piece? then soaked it in carb cleaner, used compressed air to blow out every little passage that you can find. then washed in soap and water and air dryed again? i did that twice with mine. i was sure it was clean.

if this were on a merc. there are minimal adjustments.
idle speed and mix adj.
float lever and drop adjustment
pump rod adjustment
auto choke adj.
unloader adj.
use your oem service manual to make these adjustments exactly to whatever specs is proper for you..

I'm just wondering how hard it is to rebuild a carb for someone who is very much an amateur with engine repair?

you should be alright if ya follow the instructions in your service manual. follow them exactly and ya should turn out ok.
if your following the instructions that came with a aftermarket carb rebuild kit. i've seen them and thought they were kinda generic + didn't give specs for marine application if i remember right. i used a mercrusier rebuild kit when i did mine + mercruiser instructions... i suppose it'd be hard to obtain a omc rebuild kit. but ya might be able to find the omc specs, which i'd use if i had the chance... good luck with it..

 

[John_S]

Re: How hard is a carb rebuild?

I think Ziggy has covered it well, and at this point what do have to lose, except some time? Carbs apart and kit in hand. No need to 2nd guess now. Preceed carefully and follow the directions.

 

[Provo5]

Re: How hard is a carb rebuild?

I just rebuilt my first carb last week. I watched some videos on U tube before getting into mine. I felt better about what I was doing having seen it done. Still made the mistake of mis adjusting the float levels but that is corrected now and boat runs great.

 

[fat fanny]

Re: How hard is a carb rebuild?

As the guys said take your time compare the old parts with the new and keep organized and clean. I followed Zigs lead when I did mine and it turned out just fine boat runs better than ever. But if you don't throughly clean the carb your just wasting your time I scrubbed, blew out and soaked twice also keep a clean and organized work area just like building a model car. Good luck and post back.

 

[proxyx]

Re: How hard is a carb rebuild?

when dealing with unknown issues it is a good idea to take digital pics of the item (carb) before and during the work, documenting every step as you go, it is easy then to go back to what it was, look at the manual and compare, basically there's nothing to it, take your time

 

[NW Redneck]

Re: How hard is a carb rebuild?

I've done a few carbs over the years, from lawnmowers and trimmers to cars and outboards. The last two were a homelite trimmer, and a Holley 2bbl on my OMC Ford 302. The holley wan't that bad, and from what I have read the rochesters are easier. Like ff and proxyx said, have a clean and clear work area and take pics as you go. Read through all the instructions a couple of times before you start to get familiar with all the parts and have at it!

 

[superbenk]

Re: How hard is a carb rebuild?

Well, I figured I'd document my progress visually for anyone who'd appreciate it. I've started the rebuild & posted pics online (click me).

 

[dr_bowtie]

Re: How hard is a carb rebuild?

make sure you remove the spring and check ball under teh booster assembly...

this is the check ball for the pump shot squirter (accelerator pump)...and the ball can wear goofy and the line get junk in it and then you dont get a good pump shot...

soak it good and then spray out all the passages with Gum-out and follow by compressed air...

especially the Idle circuits...

 

[superbenk]

Re: How hard is a carb rebuild?

make sure you remove the spring and check ball under teh booster assembly...

this is the check ball for the pump shot squirter (accelerator pump)...and the ball can wear goofy and the line get junk in it and then you dont get a good pump shot...

soak it good and then spray out all the passages with Gum-out and follow by compressed air...

especially the Idle circuits...

I was wondering about that. I was having a hard time trying to get it out so I kind of gave up, but if it's that important I'll try again. Should the stop at the top of the spring pry out or do I need to use some needle-nose pliers or something?

 

[dr_bowtie]

Re: How hard is a carb rebuild?

needle nose pliers and pull straight out....you should get a new T-clip in the kit so make sure you do...you dont want to damage the old one if you dont...

you want to dimple very slightly next to the edge of the clip to hold it in...tap lightly...you're not trying to drive it home just enough to hold the clip from popping out...

 

[cr2k]

Re: How hard is a carb rebuild?

There are 2 check balls. A stainless one and an aluminum one. The SS is slightly smaller and goes under the accelerator pump, the aluminum one goes under the T-pin and spring under the main venturi.

The center bolt for the main venturi has a small ring gasket that goes under it.

Any questions just ask we can get you through this.

 

[superbenk]

Re: How hard is a carb rebuild?

Well, I completed the rebuild and it seems I did ok for the most part. It seemed pretty straight-forward when reading the instructions, so I just went through the steps & got it done. I also took a bunch of pictures as I was going along in case anyone else finds them helpful. They're added to my gallery I posted a link to earlier.

It seems to run somewhat smoother now, but I still have a lingering problem that I'm not sure how to fix. When I gun the throttle it really bogs down & occasionally even stalls. When it doesn't stall, the RPMs pick up quick after it bogs for a second & then it seems to run fast & smooth. If I accelerate slowly I don't notice the bogging down. It doesn't seem to sputter at high RPMs like it was before (yay!), though I'm sure that's hard to judge fully without being under load.

If I can take any other pics or video to help illustrate my problem, I'd be happy to do so. I'd really love to get this sorted out so I can get a few more boating trips in before the cold hits.

Thanks in advance for all the help!

 

[superbenk]

Re: How hard is a carb rebuild?

Here's another question... the kit came with a couple gaskets that I didn't use because the instructions didn't really tell me to. For instance, the ventury cluster has 2 gaskets, but I only used the one I'm pointing at here: http://picasaweb.google.com/superbenk/CarbRebuild#5378410394551832690. Is that correct? Was I supposed to use both & stack them? That didn't make sense to me.

 

[Apollo75]

Re: How hard is a carb rebuild?

Hello;

Gasket is fine --- if you look at the main venturi assembly there is an open space under the gasket where that large opening in the upper gasket is anyway.

The bog sounds like you MAY have a problem with your accelerator pump --- there should be no play in the linkage --- when you open the throttle coming off idle the pump should pump fuel immediately and for a second or so. If it is just a little spurt then there is a problem.


OFM

 

[superbenk]

Re: How hard is a carb rebuild?

Posted a short video that shows the bogging issue. I shot it with the camera sitting on the back seat, so it kind of jumps around in the beginning with the engine at an idle which is probably too low.

http://www.youtube.com/watch?v=s9hiBxqEv4U

That's a potential other issue, the carb kit spec sheet says I should be idling at around 550 RPM, but my tach registers 800-900 RPM at the absolute lowest, mostly-smooth idle I can get. It *feels* like a better idle at around 1100 RPM, but that's apparently way too high, or my tach is really inaccurate. Are dash tachs known for being pretty inaccurate? It is a 30 yr old boat, do they degrade over the years? I've noticed that WOT seems to be about 1000 RPM *over* what I should expect too.

I don't have a shop tach or have access to one. Is there anything else I can check/fix to see if I'm getting an accurate tach reading or find out what RPM I'm actually getting a smooth idle at?

(Moral of the story: I need more tools! *glares at wife* )

 

[superbenk]

Re: How hard is a carb rebuild?

Hello;

Gasket is fine --- if you look at the main venturi assembly there is an open space under the gasket where that large opening in the upper gasket is anyway.

The bog sounds like you MAY have a problem with your accelerator pump --- there should be no play in the linkage --- when you open the throttle coming off idle the pump should pump fuel immediately and for a second or so. If it is just a little spurt then there is a problem.

I'll check for play in the setup. It definitely pauses before pumping gas out.

 

[dr_bowtie]

Re: How hard is a carb rebuild?

the kit covers multiple carbs so only use the gaskets that match the ones you took off...

as far as the stumble on gunning the throttle...look in the carb when you gun it to see if you are getting a good pump shot...

you did replace the accelerator rubber pump right?

as engines wear they may require more of a pump shot in which case yours isnt really adjustable...not without modding the pump itself...

a stronger spring between the pump clip and the pump rubber...this is so the pump isnt collapsing too early...

 

[superbenk]

Re: How hard is a carb rebuild?

the kit covers multiple carbs so only use the gaskets that match the ones you took off...

as far as the stumble on gunning the throttle...look in the carb when you gun it to see if you are getting a good pump shot...

you did replace the accelerator rubber pump right?

as engines wear they may require more of a pump shot in which case yours isnt really adjustable...not without modding the pump itself...

a stronger spring between the pump clip and the pump rubber...this is so the pump isnt collapsing too early...

Thanks for the suggestions. I tried taking the horn assembly off again & fiddling with the pump to see what I could find out. The new pump that came in the kit really forms a tight seal compared to the old pump. In an effort to see if this seal was too tight, I put the old pump back in and put everything back together. Unfortunately the problem still exists & honestly reverting to the old pump doesn't seem to have changed it at all (for better or worse). If anything the newer pump does produce a stronger pump of gas into the barrels, but the result was no different (same sputtering/bogging issues).

I also re-adjusted the pump linkage rod to specs according to my manual & that also doesn't seem to make any difference. Is there anyplace else it could possibly be? I'll put the newer pump back in tomorrow, but while I have it apart again, I'd like to chase down any other items anyone can suggest.

On the bright side, it really does seem to run much smoother other than this one problem!

 

[Apollo75]

Re: How hard is a carb rebuild?

Hello;

After watching the video --- you do have a problem. It definitely looks like a pump shot issue --- those are great carbs --- they do wear a lot in the pump plunger bore after years of service. The fuel goes around the pump plunger on its way down and makes the pump almost useless. The housing will generally need to be replaced when this happens.

Been so long I can't quite remember --- either there is a slot in the side of the plunger bore or there are 2-check balls for the pump shot. One opens while the plunger is returning and draws fuel in to the bore and the other --- usually in the tube leading up to the main venturi where the pump nozzles are --- is spring loaded and opens under pressure when the pump plunger moves down allowing fuel to go to the nozzles then closes by spring pressure to allow the pump to draw fuel into the bore again by the other ball.

Been a long time --- sometimes you can adjust (bend) the arm to move the plunger lower into the pump bore where it is not so lose. If there is an arm with multiple holes for the pump rod --- set it to one of the inside holes.

If all this fails --- remove the top and pump the plunger by hand and make your best guess as to whether the bore is worn or the balls are not working as they should.

Hope this helps --- A leather pump may work better if you can find one --- they expand more under pump pressure ---- lube the leather pump with oil before installing.

Hope this helps !

OFM