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Carb leaking fuel on Choke, wont run!!! 1973 20hp 200

C

cksetzer

New member
Ok so here's what I got. 1973 Merc 200, 20hp with a type B carb. Motor Serial is 3671256. I took down the carburetor and soaked all metal parts, replaced all gaskets on the carburetor and fuel pump. Put it all back on. Set the idle screw 1 1/4 out of seat. Primed up the bulb. Now here is where it gets funky. I pull out choke button and attempt to pull. After the first pull fuel starts leaking out of the carb. If I shut off the choke, no leak. Now after 1 pull with choke, she tries to fire. 1 pull with no choke she fires but only for a second. Multiple attempts and choke adjustments yesterday I had her running for a minute or 2 but I had to keep choking on & off. I know I'm missing something. Another note, when I reassembled the carburetor I blew in the fuel pump a little with the carb right side up and air went through, upside down air did not. Or vice versa. Heck I cant remember. I just remember reading on here to test it that way to make sure the float needle was seating. So what are your guys though?? Do I need to tear her back down???
 
Information is a must?----- How long have you owned the motor?----------Why was the carburetor " rebuilt "-------Was it running OK before?---------------Did problems occur all of a sudden?
 
I have owned the motor for 3 weeks. Motor has not run in a few years. I pulled the carburetor to clean and noticed the gasket for the float housing needed to be replaced so I replaced all of them while I was at it. Running ok before?? Couldn't tell you. I can tell you this. I have good compression, good spark, new fuel line from tank to motor. New spark plugs. When it does run for the brief minute or so it pumps water out the pee hole. Just an old motor I'm trying to bring back to life, if at possible.
 
The choke is working very well.---------------------Pull it over with choke " on " for 1 pull.--------Then pull without choke and see what happens.----------------------These motors had a history of bad upper and lower ball bearings. This wipes out the labarynth seal on the reed block.--------You are sure that all carburetor passages are clean ??. Spark jumps a gap of 5/16" or more??
 
yep spark jumps great. I have tried the 1 pull with choke, then pull with out. It fires, just wont stay running. Could this be its not getting enough fuel or maybe too much fuel and its flooding out. Like I said before, I can get it to run but I have to choke on and off, back and forth. If I leave it in one position she dies. I just thought that when the carb leaks fuel with choke on that my problem is in the carb?????? It pours out the opening in the front. It has me at whits end... Thanks for the replies, I believe I can get it there with all you guy's help!!
 
When a choke " works very well " the fuel will pour out the front of the carburetor. ------------" spark jumps great " is not the same as indicating that it will jump a gap of 5/16" or more. Post what gap the spark can jump !-------Then other theories can be addressed.
 
Sorry, I misunderstood what you were asking. My testing of spark plugs, was pull the plug, attach the coil wire, pull and look for spark. Now my next question is how to measure the gap?? Is there a tool that does so???
 
Ok posted too soon, Google is your friend I know. I have found a tester, 15 bucks. If there is no other way to test the gap then it looks like Im going shopping for a tester. I will follow up with my results. Thanx Racerone
 
I have a tool such as that with adjustable gaps( 2 OMC factory ones in fact )------------------laying a plug on the block is not a good test !---------You can simply make a " tool " at home ------------Need a piece of wood, plug wire .plug boot etc.---------------------Clamp pieces of wire to the wood with a gap of 5/16" .------------Put it on the motor plug wire and then to ground. Hope you get the idea.
 
Ok so made a simple version of the tester. Didn't think it would work but it did. Well I should say the lower cylinder plug had a spark gap of a 1/2" or better. The top cylinder plug had no spark at all. Even at 1/16". So is this a bad coil???
 
Swapped the power leads to the coils and found that one lead is not delivering power to the coil. One wire shows a spark jump of 5/16" or better. One wire shows no spark on either coil. So this leads me to believe the coils are fine. Could it be the power pack??? Any other test to perform to double check a faulty power pack??? Or am I overlooking something with the coil???
 
Likely the powerpack/ switch box.-----Check the ohms on the bits under the flywheel ( STATOR and TRIGGER units).-----------Likely the reason it sat around for a while because it did not run properly.---------------You may want to install a new waterpump impeller as well.-----------------The switchbox is pricey.
 
Went out to check to the Ohms and the first thing that I seen was a corroded wire with the protective cover split opened.
IMG_20101022_091443.jpgIMG_20101022_091459.jpgIMG_20101022_091516.jpg
The first pic is the wire it self, green wire. The 2nd pic is where its coming from. Its attached to the right side connection, on the pic, or if your looking at the motor from behind its on the right side. The third is the power pack which its running too. From the pic the wire comes in on the right side, feeding the power pack. Now do you think the wire can be salvaged, via cut and a new wire attached? Do you think this is causing the lack of power to wire feeding the coil? Can these power packs be rewired or just replace the unit???
 
When these wires corrode does the corrosion occur on the entire wire or just in the "opened section"? I have to head out and pick up some wire. I will repost after I repair and retest. Thanks Racer.
 
You never stated where you set the high seed jet, if in fact it is adjustable. Mercurys of that time period had very sloppy chokes. They even had to put holes in the lower cowling to drain the copious fuel.
 
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