Idle mixture adjustment???

[FJ_Russo]

First thing I did was a thorough carb rebuild and cleaning thought that might take care of my problem, now I have bee doing some reading and think it could be my mixture. I read through the sticky on how to adjust the idle mixture with the screws. But my question is... I have a VERY rich running engine. I have large amounts of gas coming out of the exhaust while running. I have owned several other engines and I know they all have some but this is A LARGE amount. My question is will adjusting these in "tightening" them lean out my engine? What would be the first thing you would do if your engine was putting out a large gas slick while running. If I run it on muffs I can see the gas coming out of the exhaust.

Thanks guys, still hoping for a boat ride tomorrow....

 

[tedious]

Re: Idle mixture adjustment???

What would be the first thing you would do if your engine was putting out a large gas slick while running. If I run it on muffs I can see the gas coming out of the exhaust.

Thanks guys, still hoping for a boat ride tomorrow....

Check your float adjustment and whether the float needle(s) are sealing.

Tim

 

[wilde1j]

Re: Idle mixture adjustment???

What engine??? Most motors in the past 30 years have all fixed jets.

 

[FJ_Russo]

Re: Idle mixture adjustment???

Its a 1974 50hp Evinrude. So my idle adjustment screws wont do anything to lean out the engine??

 

[wilde1j]

Re: Idle mixture adjustment???

You may have an idle mixture screw, but main jets are almost always fixed. Most idle mix adjustments are made from ~ 1 1/2 turns out from gently seated as an initial setting. CW is leaner, CCW is richer.

HOWEVER, see Tims suggestion, since it is not too likely the idle mix screw would cause extremely rich operation at all throttle settings.

 

[FJ_Russo]

Re: Idle mixture adjustment???

So I gave the float needles a check and if this is right I turned the carb upside down and tried blowing air through... yumm LOL and I was able to get air through. Does this mean they are not sealing and need replacement? And if so is this something that a marina will have in stock for a 1974 evinrude 50hp or this a specail order? Or am I all bass ackwards and air going through means nothing?

 

[mark1961]

Re: Idle mixture adjustment???

So I gave the float needles a check and if this is right I turned the carb upside down and tried blowing air through... yumm LOL and I was able to get air through. Does this mean they are not sealing and need replacement? And if so is this something that a marina will have in stock for a 1974 evinrude 50hp or this a specail order? Or am I all bass ackwards and air going through means nothing?

Did you replace the float needles and adjust the floats when you did the carb rebuild?

 

[wilde1j]

Re: Idle mixture adjustment???

Needle valve and seat are usually replaced together, and yes, upside down ther valve should shut off tight. Dealer will likely have a rebuild kit, as West Marine and NAPA may as well, but probably not just the needle and seat.

If you don't have an OEM shop manual, you should consider getting one. Outboardbooks.com or Ebay.

 

[FJ_Russo]

Re: Idle mixture adjustment???

These engines should not be this complicated... LOL New needles and float in the carb. The needles are sealing when I turn the carb upside down and able to blow air through when right side up. So why am I still dumping tons of gas out of the exhaust??? Anyone with some other thoughts?? I feel like I'm banging my head against the wall and getting no where...

 

[mamm7215]

Re: Idle mixture adjustment???

These engines should not be this complicated... LOL New needles and float in the carb. The needles are sealing when I turn the carb upside down and able to blow air through when right side up. So why am I still dumping tons of gas out of the exhaust??? Anyone with some other thoughts?? I feel like I'm banging my head against the wall and getting no where...

Reeds?

 

[FJ_Russo]

Re: Idle mixture adjustment???

I'm not sure what your talking about when you say Reeds? My next thought was a hole in the fuel pump diaphram allowing gas right into the exhaust??

 

[mark1961]

Re: Idle mixture adjustment???

These engines should not be this complicated... LOL New needles and float in the carb. The needles are sealing when I turn the carb upside down and able to blow air through when right side up. So why am I still dumping tons of gas out of the exhaust??? Anyone with some other thoughts?? I feel like I'm banging my head against the wall and getting no where...

Again, did you set the float heights on both before reassembly?

Is this raw fuel you are seeing coming out the exhaust? If so, i assume you have given the fuel system a good going over checking for leaks?

 

[mark1961]

Re: Idle mixture adjustment???

My next thought was a hole in the fuel pump diaphram allowing gas right into the exhaust??

Does the fuel line bulb stay firm when fully primed?

I think you would not be seeing any fuel at the carbs if that was the case but it wouldnt hurt to check and rebuild it while you're at it, at least then you know its done, eliminated as a possible cause and it wont break the bank.

 

[FJ_Russo]

Re: Idle mixture adjustment???

No the bulb does not stay fully firm when pumped. I have replaced the floats and needles on the carbs and I know they are sealing and stopping the flow of gas. And when I pump the bulb I don't overflow the carbs with gas but can hear gas shooting into the engine from somewhere while pumping the bulb my only thoughts would be through the fuel pump. If i unmount the fuel pump and prime the bulb will I see fuel coming out the back hole in fuel pump if it has leak in the diaphram?

 

[Daviet]

Re: Idle mixture adjustment???

You should NOT see any gas out of the hole that mates to the block on the back of the pump when you squeeze the primer bulb.

 

[FJ_Russo]

Re: Idle mixture adjustment???

ok that will be my next check then I believe that is where I'm losing fuel. Thank you VERY much for the quick replies and responses! I will let you know how it goes.

 

[FJ_Russo]

Re: Idle mixture adjustment???

So I finally got out of my 36hr shift at the fire station... Overtime always sounds good when you sign up for it, but sucks when the day actually comes. So I got home and checked the fuel pump. I dismounted the fuel pump from the side of the engine, squeezed the bulb and had a steady stream of gas shoot out the back side of the fuel pump. So I believe thats going to be the culprit. I looked all over for a fuel pump rebuild kit but I can't find one. Anyone know where I can get the rebuild kit for a OMC fuel pump #385781. Thanks guys!!

 

[wilde1j]

Re: Idle mixture adjustment???

Sierra complete pump:
http://www.iboats.com/Fuel-Pump/dm/*******.117646989--**********.565910743--view_id.174141

Didn't see a rebuild kit.

 

[FJ_Russo]

Re: Idle mixture adjustment???

Thank you for taking a look, that was all I found also. Surprising not to find a rebuild kit for it.. Oh well I guess I spend the big bucks on the whole pump.

 

[FJ_Russo]

Re: Idle mixture adjustment???

I just wanted to say a BIG thank you to all who helped me on this problem. I got the new fuel pump today and went for a nice ride in the boat. I need a new prop though I was running to many RPM's i had to settle for a slow cruise, I thought that might be a problem seeming how that prop and engine came off a pontoon. But no worries engine is running good and I have this forum to thank!