115 HP In line 6 carb pics

[coz]

Anyone else have this engine, please tell me if the top carb is missing a needle jet. The bottom 2 carbs have needles that the top one does not. If you zoom in close you can see there is brass in the top carb but can't tell if it broke (looks smooth, not jagged like something that broke).

I don't think the float in the top carb ever shuts off. As fuel rises, it comes out the opening where that needle should be. That needle is about 1" high, so there's no way to adjust the float an inch. If I squeeze the primer ball, fuel continuously flows out this hole.

The floats do not appear to be adjustable. Based on the other 2 carbs, it appears the fuel level should be near the top of the main nozzle which is the same as the top of the needle.

 

[canoemang]

Re: 115 HP In line 6 carb pics

You never posted the year or serial..

I checked my 84 and 86 inline 115 and all carbs for the most part are identical, looks like yours broke off.

 

[Chris1956]

Re: 115 HP In line 6 carb pics

It seems to me that my '73 Merc 850 had the brass tube at the 45* angle in the base of the carb throats, but my '77 merc 1500 did not have it an any carb. Other than that the carbs on both motors were identical.

You might look for part numbers on the carbs. Perhaps one of them deson't belong....

 

[coz]

Re: 115 HP In line 6 carb pics

This is a 1988 OB380819
The mercury parts diagram doe snot show the needles/tubes at all in any of the carbs. I did find a used carb on ebay with the exact same part number off the mercury web site and the ebay carb shows the needle. The guy selling the carb also says it's the top carb. I'm tempted to buy it, but it's $140, that' s a lot and the carb looks pretty rough.

 

[Chris1956]

Re: 115 HP In line 6 carb pics

Gee, Are you sure the float is good, adjusted correctly, the spring is intact and the inlet needle and seat are the correct ones? I don't think th elack of that brass tube is causing your carb leak.

 

[wired247]

Re: 115 HP In line 6 carb pics

Those are air bleeds. The pressure drop across them influences how much fuel is introduced into the air flow going through the carburetor. Your top carburetor may have been replaced with another carb.

It is very easy to overwhelm the needle and seat ( Of which there is no outside adjustment ) on those carbs by squeezing the fuel bowl. That outside "needle" doesnt adjust the float bowl level.

 

[coz]

Re: 115 HP In line 6 carb pics

Well I talked to 2 different boat shops and they both agreed the top carb should be same as the other 2 and there should be a needle. That needle is called an atomizer tube and it injects very tiny fuel droplets into the air stream as opposed to the larger main nozzle. My needle is broken off and I tried to remove it with a very small easy out. The easy out broke off and now that opening is completely plugged. So now the fuel level can go higher which allows the float to shut off fuel to the carb. All carbs filled properly and there was no fuel leaks into the carbs.

I test drove boat tonight and there is no difference.

I also put a clear fuel line between the fuel pump and the fuel filter. Everytime the engine bogged the fuel line was full and no air bubbles. So now I'm ruling out the fuel pump.

I was able to pattern the problem though. Boat runs perfect at all throttle positions until I idle slowly across the lake for 2-3 minutes, then if I go to full throttle it bogs down every time. If I back off and slowly go to full throttle it's fine. So, it seems that my carbs need tuned

 

[wired247]

Re: 115 HP In line 6 carb pics

FWIW, they are not needles. Needles in carburetor context are 1 of 2 completely different items. Those things you are calling needles are called air bleeds and they feed air into emulsion tubes. The emulsion tubes feed the venturi with aerated fuel.

You arent making a smooth transition from idle to main circuit. The now screwed up upper carb isnt helping anything and buying a new carb is in your future. Pick up a merc service manual and read up on idle screw settings/ignition timing .

 

[coz]

Re: 115 HP In line 6 carb pics

Last 2 nights the motor is running really good. No bogging down except in reverse. Boat starts right up, idles fine. Put it in reverse and no power, will die if I don't back off. Primer ball is firm, so I don't think it's fuel pump. Put it in forward, and it runs great.

I can't get any power in reverse past an idle. I have to float the boat off the trailer. Is there anything else that could be the cause beside a fuel issue? Could there be something in the lower unit that only applies in reverse?