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75 Mercury issuescanbt startfuel running out of carb

"I have yet to check the compr

"I have yet to check the compression...i can do that no problem but I think it would check out okay.

I have put fuel into the cylinders and have only received a pop or two out of it. Also a shot of starter fluid into the cylinders only gave out a pop.

The only time that the engine has run for a period longer than a second was when I hit it with starter fluid in the carb. I did that and pulled on it and didn't get anything but then after waiting a few minutes and trying again it ran for a couple seconds and then died.


It still just blows me away to see the fuel coming out the carb.

Yes, JB has an excellent point - it may be trying to exhaust when it should be "breathing" or something in between....

This is stuck in my head. I was screwing with it today and while I had the carb off I put my hand in front of the hole for the carb in the manifold and it seemed to be blowing air out of the hole when I cranked the engine. Shouldn't it be sucking air in? I am going to look into this more.

I was thinking of rigging something up to see whether the carb hole is exhausting air or sucking air in...something with a vacuum gage or something i dunno.

Eventually this will get figured out...}"
 
"I did a compression test toda

"I did a compression test today and both cylinders were consistant...after a pull on the cord each was around 80 lbs (approx 30 lb increase each compression)

After some messing around I determined that there is in fact suction at the intake manifold.

I took the carb apart again. The only thing that caught my eye as far as in the carb was the idle tube. The end of it just looks funny but there was no blockage for the hole all the way through. Here is a picture of it just so you guys can see:

http://i5.photobucket.com/albums/y163/green1717/IdleTube.jpg"

Now, the weird part. I realized that there is only one port on the intake manifold. I was under the impression (from this post and from the manual) that there should be two. One for the fuel pump and the other for...what I think has something to do with the idle screw adjustment....?

So, my intake manifold has only one port, but my carb requires two. This is confusing. Why would there be only one port on the manifold but then two on the carb. I took some pictures of both the carb and the manifold...

http://i5.photobucket.com/albums/y163/green1717/Carb.jpg"

http://i5.photobucket.com/albums/y163/green1717/IntakeManifold.jpg"


After all of this it just seems that the gas is not being atomized enough and it is just dripping out of the main fuel tube...."
 
jstluise said:
"I had some time today to look

"I had some time today to look at the motor. My dad insisted that it is the carb because...well he is stubborn. After talking to the local marine dealer and hearing the guy say that he has never heard of the reeds fouling, my dad won't even think about that possibility.

Just to make him happy I took the carb off again and disassembled it completely (following the guidelines in the book). The needles all looked good and I couldn't see any blocked passages. This carb is clean. The only thing that seemed funny was that the book said there is a spring that goes somewhere with the valve for the fuel bowl (the fuel inlet valve that is controlled by the float). Mine just had the valve, but no spring anywhere. I think the spring just keeps the valve open (unless the float has it closed), so this shouldn't affect anything right now.

Got it all back together and tried to start her. Oh, and I got new plugs too. Same result. Pulled on it a few times and eventually fuel came out the carb.

The plugs seemed just as clean as they were when i put them in...one seems to have a little bit of something on it.

I checked the timing like you guys said and everything seems good."
Click to expand...
(Rcycwoodlot here) I have the same motor, my 7.5 Merc. ran great when stored but after about 15 years I tried to get it running, it has given me all kinds of trouble. I got tired of pulling the recoil and took it off and used an electric drill and socket to the flywheel nut to crank it over. To this point I've got it to run but only on the bottom cylinder and with it running removed the top plug wire, connected another plug to the wire only to see constant spark but it still does not fire on the top cylinder. I did the compression test on both cylinders with about 125 psi. on each cylinder. I have replaced the ignition module, spark plugs, and have had the carb off more than 6 times checking for problems with no answer to why it may start or not start. With the carb off you can see the reed valves for the bottom cylinder, but I haven't taken a mirror to look up at the top reed valves. My motor may run for 10 seconds or 10 minuets at idle or half throttle, in gear or not, when it gets a notion it just stops and that top cylinder spark plug never stopped sparking until the motor rotation stopped. Good luck on your project, I'm still looking for answers on mine.
 
I doubt the folks from 16 years ago are still stumbling about on that motor !!-----Woodlot , does the spark jump a gap of 5/16" or more on both leads.
 
racerone said:
I doubt the folks from 16 years ago are still stumbling about on that motor !!-----Woodlot , does the spark jump a gap of 5/16" or more on both leads.
Click to expand...
I have only tried it with the spark plugs, but it is a sharp blue spark and my spark voltage tester read about 12 thousand volts when running. After it stops it may restart or not, but it always has spark. If the reed valves on the top cylinder are ok and not leaking back pressure to the carb, is there a possibility the magnets in the flywheel got weak from sitting for that long?
 
When I get back at it that will be my next plan of attack, that's about all that's left. I was wondering if the seals may be an issue after sitting that long. Thanks for the input!
 
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