for the mercarb geniuses...intake flooding

got a mercarb 2bbl sitting on a merc 3.7 165. intake keeps flooding mercilessly just while cranking. (engine will kick a few then quit) to make a long story short..the fuel pump is fine..the carb itself isn't flooding but it sends all sorts of fuel into the intake. I intend to take the carb apart tonight...but I do notice that each time I pull it apart..the power piston comes right out loose...just as if it was sitting on the power valve all the time (so..I am figuring that the engine vacuum should keep it from doing that)

If I peen that thing in place so it keeps from falling out..am I on the right track to resolving this issue? I am tired of cleaning up my intake from 1/4 to a 1/2 inch of fuel every time I crank the starter!

thanks guys..hope there is an easy answer to this one

IMO, there is a problem with either with the float, needle valve, and, or, it's seat, it's not sealing,,, and gas is just being continually pumped in by the fuel pump. It could be a float that is sinking (not floating), for some reason, (usually only if it's hollow metal), or the needle valve above it is not seating because it's out of alignment, or, the needle valve is damaged at the tip Or, there is a piece of debri in the seat holding the float open! (I've personally seen all these sporatic things happen over the years).

Take the carb apart, and check all these items, even the brass needle seat can usually carefully be unscrewed to check. I'm not sure about the power valve without seeing up close what is happening? Can you put up some pix of it maybe?

MikDee said:

IMO, there is a problem with either with the float, needle valve, and, or, it's seat, it's not sealing,,, and gas is just being continually pumped in by the fuel pump. It could be a float that is sinking (not floating), for some reason, (usually only if it's hollow metal), or the needle valve above it is not seating because it's out of alignment, or, the needle valve is damaged at the tip Or, there is a piece of debri in the seat holding the float open! (I've personally seen all these sporatic things happen over the years).

Take the carb apart, and check all these items, even the brass needle seat can usually carefully be unscrewed to check. I'm not sure about the power valve without seeing up close what is happening? Can you put up some pix of it maybe?

Click to expand...

I believe Mike pretty much covered it....and either the carb is flooding or your fuel pump diaphragm is faulty and sending fuel down the throat of the carb. Best I remember, the power valve actuator is staked in place. Use care when you stake it as it is supposed to move up and down via a vacuum signal it receives. Do you have a manual?

OK well guys..had my AHAAAA moment the other night... and indeed that was the issue. each time I took apart the carb..the power piston fell out..... so...each time I put it on the intake..and cranked away...the power piston was resting on the power valve! so....go figure...all sorts of fuel was going straight into the intake... sure...crank it again! more fuel anyone????? so....word to the wise (and it doesn't get covered too many places) if you DO carburetor work...make SURE if that does come out easily...that it gets FULLY seated (and even peened if needed) into its recess or you will surely have some extra fuel in the intake....

I tried to upload the pic but its nothing extraordinary.. just me holding the piston. rem the issue I was having was not the carb flooding..but the intake. had nothing to do with the needle and seat. The engine started last night..but with all my futile attempts to figure out why all this was happening..killed my battery. Now I gotta see if my wife can go get a battery charger from somewhere so when I get back home we can go throw some kids off a tube behind our boat !

That's great John....heck yes, get out there and have some FUN!

Good for you! Thanks for letting us know. By the way, make sure to change the oil, if you suspect (smell) gas in it.

well got things started of course (finally) and got the family out on the water... made a few notes along the way....

hesitates at about 2500.... smooth acceleration.. (I ran it with an older, slightly stiffer power valve, so I am going to put the new one in and see how it does)

idles ...ok. probably a bit on the low side slightly rich. not enough to justify me even touching the needle, seat, and float any more.... that I have checked plenty.

I was checking up on a few other posts from people with similar issues... seems a recurring theme is the dist. advance weights sticking...rusting... given that this thing was run for years in salt water and I have cleaned up plenty of garbage out of this engine... it wouldn't surprise me that it is hiccuping smooth acceleration and my ability to gun it.

oh well...if you guys have any more thoughts on that ..send them my way. the more I ran it the other day (we were out for about 3 hours) it ran better. the kids had a blast.

In the bottom of the Dizzy, are the weights & springs for the centrifugal advance. If you take off the Dizzy breaker cam (usually a spring clip, in the center), you can get at them to clean up, lube, fix, or repair till they move smoothly for the full range of motion. This should really wake your engine up, if they haven't been working correctly.