Mercury 115 horse carbeurator leaks

[Marty Adam]

All three carb were leaking from the front and bottom plugs. I removed all three and installed new gaskets and silicone sealer. All tree quit leaking from those points.

When I removed the carbs. rather than removing the fuel lines, I took the top off of the float bowls that hold the needle valves. I replaced everything and ran the motor. It ran fine, and started easily. Now fuel is dripping from carb throat. I shut off the engine and tilted the motor up. Fuel leaked from two of the three. The floats are not scaled, but are brown. Are they not working properly and have to be replaced or is there an adjusment to be made.

The carbs were rebuilt in a shop. It took almost all summer and I do not need the headache of taking it back if I can fix the problem myself. They charged me very little due to the time and problems that they had.

 

[sschefer]

Re: Mercury 115 horse carbeurator leaks

The problem described as fuel dribbling from the carb throats could or might be caused by one or a combination of the following:

1. Too much fuel pressure (over priming by squeezing the bulb too hard).
2. Faulty needles or needle seats in the carb bowl.
3. Improperly adjusted float.

I am curious about the prior leaking problem since I've never rebuilt any carb that required the use of anything other than the gaskets to create a leak proof seal.

 

[jeff_smith_0423]

Re: Mercury 115 horse carbeurator leaks

Mercury side bowl carbs tend to drain when the motor is lifted. Quite sensitive. One lovely quirk on the big inlines.

 

[Marty Adam]

Re: Mercury 115 horse carbeurator leaks

The problem described as fuel dribbling from the carb throats could or might be caused by one or a combination of the following:

1. Too much fuel pressure (over priming by squeezing the bulb too hard).
2. Faulty needles or needle seats in the carb bowl.
3. Improperly adjusted float.

I am curious about the prior leaking problem since I've never rebuilt any carb that required the use of anything other than the gaskets to create a leak proof seal.

The front and bottom plugs underneath the thoat were leaking. There were fiber gaskets on the front one and nothing on the bottom. I replaced the fronts with a rubberized gasket that I made. I put a thin layer of silicone sealer on to help. The bottom plug did not have a gasket. I put a light coating of silicone on those before replacing them.

 

[sschefer]

Re: Mercury 115 horse carbeurator leaks

Re sealing: That should be fine, I would have probably chosen a rebuild because I'm a nit-picker but if it works for you then what the heck.

You may want to think about rebuilding the carbs sometime in the future and in fact if you find that you can't get the dribbles to stop you may have to anyway.

If that ends up being your solution then you probably want to get a Service Manual. The Merc Service manual has step by step procedures for rebuilding the carbs that are very easy to follow.

 

[Jeff_G]

Re: Mercury 115 horse carbeurator leaks

Remove the silicon seal. It breaks down in fuel and you can get small pieces into the carb and clog a jet. You can get the proper gaskets from any outboard shop. Just a couple dollars.
Yes they will drip some fuel when trimmed up, there is a small square catch basin underneath.
To check your float level remove the float bowl covers. Turn them upside down and the top lever, upside down, should be level.
Drop the floats in a small container of gas and make sure they float. When replacing them make sure they slide easily and down on the alignment rod in the float chamber.

 

[jeff_smith_0423]

Re: Mercury 115 horse carbeurator leaks

The floats are about $9 apiece. If you're checking them, you might as well replace them. I replaced two on a 90hp that I owned, six weeks later the third went bad.

There's no substitute for proper parts. Complete carb kits go for around $18 and you won't be chasing problems if your own creation. The side bowl carbs are just about the easiest thing to clean/rebuild that you're going to find.