Carb Rebuild

[FreeBeeTony]

I rebuilt the carb today. I have been told it's a Weber/Carter/Edelbrock....one or the other I guess, The number stamped on it is 2631 9770S. <br /><br />The rebuild was rather painless. The carb was filthy. I was sure this was my problem..........<br /><br />However, just got back from a test run and it wasn't much better. I had my wife run the boat while I looked into the carb. It seems like the secondaries need to open earlier. I didn't see any fuel coming out of the secondaries. I then had my wife slow down into neutral. I got a screw driver, and as she accelerated in gear I listened to the engine, when it began to "sputter" I stuck the screwdriver into the secondary throttle plates, and started to open them. I then saw fuel coming out of the secondary venturies.<br /><br />I am going back down to the boat to get the carb.........

 

[ziggy]

Re: Carb Rebuild

freebeetony, i don't know what the proper way to do it. perhaps wait for your new service manual to come so you have some info & facts, i don't know. but it sounds like you have yer face right over the carb while it's running, w/o the flame arrester on it so you can look for fuel. sounds a little dangerous to me.....what will happen if it backfires thru the carb with yer eyes down close to see if fuel is getting into the secondarys....... just some food for thought. who knows, maybe my notion is all wrong, then again, maybe not.........

 

[FreeBeeTony]

Re: Carb Rebuild

OK...I re adjusted the carb per the directions in the rebuild kit...it looked like the secondaries were opening too early, according to the kit the secondaries should open when the primaries are open by 13/32". Mine were opening at ~8-10/32". I reinstalled and took it for another test run...........didn't seem to help much. It rune smooth up until 3200-3300RPM, then it starts to sputter.....<br /><br />I need help..........I also noticed fuel coming out of the pump jet housing......I thought fuel should only come out of there when you pump the throttle.<br /><br />It definitly seems to be a fuel related problem, when I played with the seconadies while my son was driving, I could change the performance.<br /><br />Now I need help fine tuning this thing.

 

[Phantom17]

Re: Carb Rebuild

I hope for your sake that thing don't backfire on you dude. You'll lose more than your eyebrows. Be careful. Use a mirror on a stick if you need the flame arrestor off.

 

[FreeBeeTony]

Re: Carb Rebuild

How about the timing? IT's the Thunderbolt IV ignition. Is the spec 6* BTDC at what RPM? I am going to check this next.......

 

[Bondo]

Re: Carb Rebuild

I can't help you with a Motor Manual,........<br /><br />But,... If This Link works,......<br />It's a Great Manual for Your Carb.........

 

[FreeBeeTony]

Re: Carb Rebuild

That's a great link bondo!!!<br /><br />I will check it out today.<br /><br />How about the timing? Is it 6* BTDC?<br />Can I just check it normally? It's a Thunderbolt IV....<br /><br />More info......when running the boat.....it doesn't seem to have the "draw" in the carb......if I put my hand over the carb I can almost feel the mist of fuel.......doesn't seem like the fuel is being "pulled" into the carb.<br /><br />I described this to a friend of mine (race car mech), he said it could be the cam.....I am thinking/hoping I have a stuck exhaust flapper.

 

[FreeBeeTony]

Re: Carb Rebuild

^

 

[tommays]

Re: Carb Rebuild

tony<br /><br />i think you going to drive your self crazy trying things without the manual<br /><br />after all you did on the first boat if you wait for the manual and follow it i think it will take you to a happy ending in a step by step manner<br /><br />tommays

 

[FreeBeeTony]

Re: Carb Rebuild

I don't think the manual is going to help troubleshoot this problem.<br /><br />And I ordered the MERC MANUAL.........

 

[dutch135]

Re: Carb Rebuild

Tony,<br />Is there a chance that the carb can still have some blockage somewhere? When you rebuilt it,<br />did you go thru it completely? all new parts, nozzles,, etc? <br />I just cleaned one and didn't change out any parts, found plenty of crud causing my problems with the accelerator pump. Took the carb off and tried cleaning everything the best I could without tearing it completely apart and soaking it.

 

[FreeBeeTony]

Re: Carb Rebuild

I took the entire carb apart, replaced all gaskets, accel. pump, float valves and readjusted floats, etc...

 

[dutch135]

Re: Carb Rebuild

What did you do to clean any internal parts?<br />compressed air? soak the carb in solution?<br />Just trying to make sure that the carb<br />is completely clean thru and thru... in all<br />it's nooks and crannies...

 

[FreeBeeTony]

Re: Carb Rebuild

3 cans of GumOut and compressed air.

 

[dutch135]

Re: Carb Rebuild

cool,<br /><br />that's how i did it also... making sure all the nozzles etc were clean.. one needed a wire to get cleaned at first...<br />i'm out of suggestions...

 

[Bondo]

Re: Carb Rebuild

Ayuh,.........<br />I'm Glad you liked the Carb. Manual..........<br />

How about the timing? Is it 6* BTDC?<br />Can I just check it normally? It's a Thunderbolt IV....

Ayuh,.......<br />At the right rpms,....... No Jumper Wire Needed.....<br /><br />I'm not sure of the spec. on Your motor,.....<br />But I've Never seen a SBC that wouldn't Run Just Fine, when timed to 6*, or 8*.........<br />Anymore, You have to be Careful,.....Spark Knock.......<br />Any Less,.... It'll be a DOG......<br /><br />Good Luck...

 

[FreeBeeTony]

Re: Carb Rebuild

Thanks bondo, <br /><br />I checked the timing tonight........seemed kind light at 2* @ 600RPM(if I was reading the marks correctly, is the big opening 0* and each point 2*?). I advanced it to ~6* and it seemed a little better, maybe I will go to 8* tomorrow.<br /><br />Still not right though.....won't go past 3500 RPM's and the carb still isn't right. <br /><br />How do I know which carb I have in that manual? The number stamped on my carb is 9770S.

 

[dutch135]

Re: Carb Rebuild

Is this the carb you have? It references a 9770SA,<br />but seems to fit into your year/make and model.<br /><br />www.<br />mercruiserparts.com/Show_Pictures3.asp?dnbr=816596&ivar=images/CRUISER/816596/15.png&inbr=1014&bnbr=160&bdesc=CARBURETOR+%28WEBER%29<br /><br /><br />sorry i can't seem to get the url to work right

 

[FreeBeeTony]

Re: Carb Rebuild

that looks like it.......

 

[tee-boy]

Re: Carb Rebuild

I like those edelbrocks.