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Starting a Mercarbbed engine

bulit7

bulit7

Contributing Member
"Guys, what is the correct pro

"Guys, what is the correct proceedure for starting a Mercarb cold and warm?
Thanks!"
 
"Bulit7
IMHO on a cold engine

"Bulit7
IMHO on a cold engine pump the throttle one time to load up the choke and give the engine some raw fuel.
On a warm engine all should be in a ready state to run, just turn on the key.
Bert"
 
I agree w/Bert. I also place

I agree w/Bert. I also place the throttle slightly past the point of idle position; about 1000 RPM and pull back after a few seconds when it starts. My engine is an 87 4.3L.
 
I always did the following wit

I always did the following with good results to start a cold mercruiser.
*disengage the transmission (button on the side)
*advance throttles all the way and back to idle(sets choke and primes with fuel).
*start (at idle).
*advance slowly to 1200 or so to fast idle it for a minute.
*Go below and get a cold beer from the fridge.
*Pull back to idle and let it warm up.
 
Well I have a question for you

Well I have a question for you carb guys. I have a 1978 Sunrunner with a GM straight six. It will not start unless I poor gas down its throat and then it will die. I drained some fuel out of the bottom of the tank to check for water. Got a tiny bit. Installed a new fuel/water sep filter. Pulled the top of the carb off to check for junk. Not too much found. There is rust in side the body. Any ideas if what to do. I put all new plugs wires and coil on. I have had it running no more than 10 sec.
 
Allen Ellzey
First off check

Allen Ellzey
First off check your fuel pump pressure and flow rate to make sure you are getting a good supply to the carb. If the pump is putting out go after the carb and possibly do a rebuild.
Bert
 
"[b]"Not too much found. T

""Not too much found. There is rust in side the body."

Ayuh,... It only takes 1 tiny piece...

Doesn't that carb have a Filter in it's inlet,..??
I Believe the Fuel Pump also has a Filter in it..."
 
"Pulled the top of the car

"Pulled the top of the carb...There is rust in side the body."

I'll bet that it's not rust but granular varnish that comes from old fuel. Most "old" carbs will have some in the bowl. The finer bits will plug idle circuits.

Follow what the gents stated above. I would rebuild the carb and fuel pump since it will also be full of the granules. Check the sight tube nipple on the fuel pump for varnish/gum. If it's there then the pump needs to be cleaned or replaced to get rid of it or it will keep getting into the carb.

You may need to clean the fuel tank since it may have varnish crud on the bottom. Dump a couple cans of SEAFOAM into the tank and add some fresh fuel. It will dissolve some of the varnish in the fuel system and also remove water.
 
"The fuel pump is woking good.

"The fuel pump is woking good. That was one of the first things I did check. Sorry for not posting that before. I was thinking rebuild on the carb. The problem I have there is someone took the ID tage off, all I know is it is a Rochcster 2 brl. The guy I bought it from said he recommends the accel pump be replaced. As far as the rust, it was not in the bowl but in the throttle body (I guess that is what it is called). I know fuel injection way better than carbs. Thanks for all the imput. I will just have to pay for a rebuild."
 
"Allen, Look for a number sta

"Allen, Look for a number stamped on the side of the float bowl and bring that number to an auto parts store and get a rebuild kit. Simple carb that you can rebuild yourself. I use Carquest auto and when I open the box it has a Sierra kit inside. Napa is good too."
 
You might consider just replac

You might consider just replacing the carb w/a Merc. reman. due to the age of it if it is the original. Bushings are probably well worn.

It is an easy carb to rebuild. Naval Jelly will take off the rust. Get the right carb base gasket; very imprtant. Use specs. for setting up the carb from a manual and not the kit.

OVERHAUL KIT 823427A1

CARBURETOR ASSEMBLY 1351-7356A1

Insert the numbers above in the "Engine Parts" search.
 
Just cureous. Do you have a m

Just cureous. Do you have a mercarb with 1 idle adjustment screw or a rochester with two adjustment screws?
 
Mine is the Rochester with 2 s

Mine is the Rochester with 2 screws. I just tore it down and put it in the buckt of carb clean. I am gonna let it soak for a day and then pull it out and see what I have. I did notice that one of the ports for the adjustment screws was plugged up. Might have something to do with the run problem. They guy I got it from said he rebuild the carb several years ago. It looks overall in good shape. Just junk in it. I will let you all know as I get more done on it.
 
Blow it out w/compressed air a

Blow it out w/compressed air and she'll run fine. Hardened varnish deposits stuck in the idle circuits can be removed by boiling the carb in a pot of soapy water for 20 mins.
 
"Boiling a carb for 20 min in

"Boiling a carb for 20 min in soapy water, I have never heard of that one before. I have it torn down in a bucket of carb dip will reassemble in a day or 2. Great info from all of you."
 
"Allen,

Before reassem

"Allen,

Before reassembly make sure the power piston moves freely. The power piston is that long rod sticking out of the air horn (carb top). It pushes the power valve. A nasty flooding condition occurs if the piston is stuck. You don't have fiberglas fuel tanks do you? (The guys here know where I'm going with this question.)"
 
"Allen,

The year of your bo

"Allen,

The year of your boat is in or near the era when certain resins in the fiberglas would disolve when E10 ethanol fuel was added. The disolved resin would clog filters, gum up carbs including glue the power piston in one place and sieze engine valves to their guides thus bending pushrods. I learned the hard way. I have not heard of any Searays with the proble so you are probably fine."
 
Well that is a good bit of inf

Well that is a good bit of info. Mine is a Sunrunner. I will check the tank one of these days. The guy I bought it from said the carb as been rebuild twice while he had it. He had this boat for 95% of its life. It seems to run great when it does run. Just without pooring fuel straight down it doesnt run for long.
 
E10 fuel came out 2-3 years ao

E10 fuel came out 2-3 years ao. I'm pretty sure you don't hava a problem. Depends all on what resin was used. Bertrams were hit really hard with the problem as was my Jersey. There is a class action suit in CA. If you've run through a full tank without a problem you are probably okay.
 
Well here is the latest update

Well here is the latest update. I put the carb back together and it will start and idle pretty good. It wont rev up yet but I have to mess with the mixture screws. I am so excited to finally have it up and running. Thank you again all.
 
"Allen Ellzey
The mixture scr

"Allen Ellzey
The mixture screws won't do much for your high speed problems. I'd start by checking compression, timing, plugs/wires, if you're sure the carb is functioning properly.
Bert."
 
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