Fuel Pumping Out of Hole on Bottom Carb - 45 HP Merc

[achilles555]

I have a 1987 Mercury Classic Fifty 45 HP. Been having problems getting on plane, and won't throttle past 3000 RPM when in gear.

Started happening after I had the carbs rebuilt. I had a stuck float, so there was gas pumping through the carb every time I turned the motor.

I took the boat out today, and tried again. I fixed an electrical problem (bare wire on black/white from trigger). Thought that may have fixed it. Still have the problem.

Started it up, and took the cover off to see what was going on while running. I now have fuel pumping out of a hole on in the bottom carb. the hole is on the upper right side of the carb, just above and to the right of the shutter plate.

When started, the carb is sucking the gas through the shutter plate. When I pump the bulb, it won't get completely hard, and gas pumps out of the same hole.

It looks like the top carb has a slotted screw in the same place, but it's hard to see. It looks like the bottom carb has an extra hole...the one that all the gas is coming from.

I believe this to be the cause of my bogging/RPM problem. When I pulled the plugs, the #4 cylinder is washed clean. This would confirm WAY too much fuel is getting to that cylinder.

Not sure what to do next, or what this hole in my carb does? Any help/guidance would be greatly appreciated. AC.

 

[achilles555]

Re: Fuel Pumping Out of Hole on Bottom Carb - 45 HP Merc

i found photo of carbs similar to mine. my carbs have the round float bowl. click on the link below to see. hopefully this will help . thanks again, ac.

http://img.photobucket.com/albums/v11/scleme1/carb1.jpg

 

[sportsmanphil]

Re: Fuel Pumping Out of Hole on Bottom Carb - 45 HP Merc

Sounds like you have an inlet needle sticking open.

 

[verado7]

Re: Fuel Pumping Out of Hole on Bottom Carb - 45 HP Merc

pull the carb apart again and bend the float tab so that you get the floats level or slightly below level with the bowl and do this with the carbs upside down - the float is too low in the bowl right now and not seating the needle - before you re-install hook up the fuel line and pump the bulb firm and hold for 20 seconds - no fuel should come out - but it is normal for fuewl to drip out when the motor is tilted up not running .i have the 88 year same motor - dont worry about the float measurement in the book .

sorry had to edit my own post ..... if this doesn't cure it that float might have a pin hole in it and you can check by dunking in a bucket of water and see if it fills up .

 

[achilles555]

Re: Fuel Pumping Out of Hole on Bottom Carb - 45 HP Merc

thanks for the help, guys.

verado - i had another guy rebuild my carbs because i was under the impression that they are hard to get to. have you had yours off? are they hard to get out? is this something a guy could do pretty easily? thanks again, ac.

 

[verado7]

Re: Fuel Pumping Out of Hole on Bottom Carb - 45 HP Merc

if you comfortable with working on carbs then yes - if you want to learn take it slow and get a manual - incase you forget where something goes - you take that front bracket that the front cover attaches to off 2 bolts on bottom 2 nuts on top then you can get at the carbs - i do mine every few seasons just as preventive maint. and as a note stay away from the new "enviro-fuels" they eat rubber which is the tip on the needles .

i should also mention when you get them apart lokk and see if theres some crud keeping them from seating properly - it only takes a minute spec of sand or ??? to do it .

 

[achilles555]

Re: Fuel Pumping Out of Hole on Bottom Carb - 45 HP Merc

thanks verado. i took the carbs apart over the weekend, and inspected them for problems. they were very clean (just had a rebuild), so i bent the floa tab very slightly on the one that was leaking the fuel. put everything back together and it seems like i may have fixed the problem. i haven't had a chance to take the boat out to the lake again to test it out, but it looks promising. when i pump the bulb, it gets hard after a few pumps...and no fuel is coming out of the front of the carb.

i'm so glad i decided to take the carbs apart myself. i learned a lot about how the fuel system works, and i can now do a rebuild for around $20...whereas it just cost me $230 to have them rebuilt.

thanks again for the help. ac.