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Merc 350 carb rebuild

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79century

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"hi all,

i have a merc 350

"hi all,

i have a merc 350 (260), an 898 outdrive, 2 bbl rochester carb. i just rebuilt the carb w/ a mercruiser rebuild kit. i have several questions.

below the accelerator pump there is a steel ball (looks like a bb). my old one was corroded in place. it was so bad i had to use a pick and dig out the junk/rust/debris just to get the ball out. i have gotten the hole this ball sits in as clean as possible, and from what i can tell it doesn't go anywhere. that doesn't make sense since there was a check ball in it. should i take the carb back apart now that i've picked that ball and crud out and re-soak it? all the passages came out nice and clean after soaking and blowing out w/ comp. air, except for this one. i guess because it was so caked up the soak must not have penetrated it. the rebuild kit said there is a retainer on some models. but the ball it said is standard (didn't specify ball to only some models). i didn't see a retainer in mine, unless it was disintigrated. so, is it possible that it's a blind hole (dead ending) or does it have to go somewhere? should i re-soak to open passage? can ball be placed down in hole with no retainer?

i appreciate the time you all take to read and answer our posts."
 
"also, there is ball/spring/re

"also, there is ball/spring/retainer assembly in the carb. (this is separate from the above mentioned item). the retainer is "T" shaped and is swedged into the casting. i don't know what you call this, but i didn't remove it before i soaked the carb. i soaked the carb before i got the rebuild kit, and i didn't think it was an item that should be removed since it was swedged into the casting. now that i have the kit, and can see that theres a ball and spring under it, i am worried that it may be cruded up like the other one that i found. should i remove this assembly to make sure the pasage is clear? is it an important feature?"
 
"The ball in the bottom of the

"The ball in the bottom of the accell pump acts as a flow limiter I think.

yes you need to clean the passages where the T shaped peice is, as this is part of your accellerator pump passagem definately an important feature. Did you remove the 3 brass fittings and clean inside them? especially the one with the little pin in the middle, you should have a new one in the kit."
 
brian is right its very import

brian is right its very important that that passage is clear or its just the same as not haveing a acc pump. it works in sinc with the jets and is accualy the brain of the carb sorta speak lets it know what the demand is
 
"thanks brian.
i guess i'

"thanks brian.
i guess i'm gonna just go ahead and take it apart again and re-soak it with that stuff out. yea, i removed the 3 brass jets, plus the brass thing with the pin and spring in middle. i got a new one like you said. i didn't get the 3 jets in the kit. i was hoping i would. they look to be in ok shape. there is a discoloration on them. is it fuel varnish? does this need to be cleaned off? can i put them in the carb solvent? also, once i remove that t shaped retainer and spring and ball, to reinstall, should i re-swedge it into the casting with a small chisel and hammer?"
 
"you can definately soak the 2

"you can definately soak the 2 jets in the kit, the peice with the pin is called a power valve, cleaning the jets will restore the orifice to the proper size and maitain the right amount of flow.

to keep the T in the housing, yes just tap lightly on the housing with a small chisel just enough to deform it to keep it from coming back out during install of the venturis(the peice that screws down onto that section), which you want to make sure that is as clean as you can get it, as there are 2 holes and passages on it, that the accel pump pumps the fuel through. you might have more than 1 gasket for the venturi section, only 1 should fit and not block any holes.

did you get 2 new idle mixture screws ? (good kit if you did) did you soak the base and blow the holes there too??

The important section is the accel pump and venturi and under the T.

Careful when installing the accel pump into the tube, I had one rip on me.. glad it was my own carb and not a customers."
 
"ps.. you dont want to use any

"ps.. you dont want to use any wire to clean the jets, you dont want to damage them"
 
"brian,
i'm gonna soak th

"brian,
i'm gonna soak the jets and power valve, along with the section of carb that has those 2 passages where the balls go (pump well and the other with t retainer) i think its the float body section. anyway, i'll also soak the idle screws & springs too, since my kit didn't come with those... as far as the base and the rest of the carb, it cleaned up really good. i work in an industrial plant, and used an ultrasonic bath with some super cleaner in it. it heats to 170deg. F. the guys in the shop said it was safe for the carbs. then i blew it out and out and out. so, i feel good about it all except the problem areas that u have helped with. again, thanks for all help, and i'll let you all know how it turns out."
 
"The corrosion you have found

"The corrosion you have found in the check ball and carb base comes from water in the fuel. W/every 30 gallon fuel fill up I always add a can of fuel preservative w/a water dispersant. You never know when your boat is gong to end up sitting for a long period.

"i'll also soak the idle screws & springs too, since my kit didn't come with those... "

Don't mess with them; buy new needle valves and seats since the old are damaged.

"t shaped retainer and spring and ball, to reinstall, should i re-swedge it into the casting with a small chisel and hammer?"

No hammer & chisel to swedge it. It's soft metal so just use an awl or pointed tool and press it with your hand to swedge it where the two pieces meet.

"there is a discoloration on them. is it fuel varnish? does this need to be cleaned off?"

Yes, clean it off. I use a cleaner called Deep Creep made by Seafoam; works great on tiny fuel passages and parts."
 
Remeber not to do anything to

Remeber not to do anything to the inside of the jets that may make the distorted as like brian said they are an orfice and the inside diamiter is critical
 
"ultrasonics cool !! nice tool

"ultrasonics cool !! nice tool for the belt, I lightly take a scotchbrite pad to the tips of the needle valves to sometimes clean them up.

an awl's good like guy said, or straight screwdriver, a gentle single tap is usually plenty, again it's just enough to hold the T in place while you put the venturi peice in."
 
"great info guys.
i took it

"great info guys.
i took it back apart. i'm going in to work in a bit so i'll soak it again then.

guy, i tried to find the jets, power piston, and idle adjust screws online at mercuiserparts.com, and a few others, but couldn't find them. if you have a part number for those it would be great. i would definitlety rather replace them than clean up old ones.

also, the ball in the bottom of the accelerator pump well is about 3/32" dia. it fits down in that hole fine and is not real sloppy, but should there be a retainer over it? when the pump rises won't the ball want to pull up out of the hole? i didn't get one in the rebuild kit. the paperwork said there is a retainer on some models, and i couldn't tell if there was a rotted away retainer clip in the gunk i dug out of the hole.

also, should the 2bbl rochester have a 1/4" gasket under it like i read about with the mercarbs? are these basically the same carb? my kit only came with a thin gasket."
 
"for the ball, the accel pump

"for the ball, the accel pump spring holds it in, no clip. I think you might have a hard time finding the jets and power piston, see if there are any carb shops near you. I'd go with the 1/4" gasket if you can get one, check at a local auto parts store, the 2bbl rochester and MerCarbs are nearly identical, I beleive Merc bought the patent, but i'm not sure."
 
"yea, i see what you mean abou

"yea, i see what you mean about the spring keeping the ball down in that hole. the problem is, (and i know your gonna tell me i'm wrong), but that hole just does'nt seem to go anywhere. i soaked the part again. blew it out good. the hole is nice and clean now. i made a small pick with a slight bend on the end so i could feel around the sides of the hole and make sure that gunk wasn't creating a "false surface". and i swear it appears the hole goes nowhere. i can see by the outside body of the carb where it would go. it would go to a tube that comes back up in the float area. which makes sense. - the plunger goes up, the ball lifts allowing fuel in. then the ball drops, closes off the passage. the plunger comes down and pushes the fuel up into the venturi. it all makes sense, except the hole dead ending. theres a slot in the plunger well. is it possible on this model the fuel just enters the plunger well via that slot, and not the hole in bottom? but still, if this were the case, why would there have even been a ball in the hole? i'm confused..."
 
"hm, maybe you could put some

"hm, maybe you could put some simple green or other penetrant in there that doesn't evap quickly see if it works its way in the hole ? I dont want to suggest you remove the plug from the tube end and check it, I've used a comp air blow tool with a rubber tip to blow that out before and had air coming out where the T bar was, maybe you could blow from the T bar back? (i've done that too.. ) I've only done about 30-40 of the 2bbl rochester/mercarbs(it's been about 9mos since I did the last one, and am pretty sure that the ball is supposed to be there, but I'm thinking that my 2bbl rochester doesn't have one..

Up near me is a carb shop called Hobb's Carburetor in Pelham NH, give them a call say a frequent customer advised you call them, just try to keep them on the phone for as little time as possible, see what they say.. they've been around for 30 years that I know and that's all they do Carbs, lots of them. I'm a little confused too.

I have my old carb in the back of my truck and might just go pull it apart to check, I also have a couple instruction sheets to.."
 
"brian, a machinist was lookin

"brian, a machinist was looking at it with me at work, and had a good point. there is no plug on the outside of the carb where that passage would have been drilled. so, theres no way it is there. the ball must have been dropped in the hole on all models. whether they needed it or not. or maybe it was assembled at 4:00 on friday afternoon! anyway, i'm not sure we're talkin about the same passage. this one is at the bottom of the pump well and goes straight down. then over just outside the pump well. then straight back up a tube that is part of the carb body in the float area. i have the hole in the well. and i have the tube in float area. i just don't have the horizontal passage connecting them. the passage to the t-bar hole is also in the bottom of the well, but doesn't go down. it just goes horizontal leaving the well. and i do have a exterior plug where that one was drilled. so, i'm still puzzled as to how gas enters the well when the piston draws up. anyway, what do you think? i could call your carb shop buddy, but as you stated his time is money, and i hate to waste it. thanks again to all."
 
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