Idle mixture screws adjustments 135 hp 1990 Mercury

[circlehook]

Hello I need to adjust the idle mixture screws on my 135 hp Mercury I Have a tachometer does this help and is there any sequence between the three carburetors
Bob

 

[Faztbullet]

And may I ask why they need adjusting??? They are preset at factory that why the tamper proof caps.

 

[circlehook]

I have very heavy smoke in the exhaust it’s brand new gas and proper oil quantity and with the air box open you could see lots of fuel flowing out of the carburetor I had them apart and set the float levels new gaskets, float & needle valves etc the only thing I didn’t do was touch those idle mixture screws is there any way of telling that is the problem
Bob

 

[circlehook]

Compression is good in all cylinders & spark also. I am going to change the plugs but there not all that old. I also linked & sink the linkage. And the timing is spot on.

 

[Faztbullet]

Did you check the thermal valve on starboard head? Does it do this after running and setting?

 

[circlehook]

I didn’t check the thermo valve didn’t know there was one. And it smokes really bad a first start up and lessen after a while but it smokes out 3 entire houses no mosquitoes here

 

[circlehook]

Oh and then at wide open throttle I only get about 19 mph where I had 25-29 at one time I thought the plugs might be getting fouled at the initial start up

 

[racerone]

If fuel flows out of a carburetor you need to look at float and float valve.

 

[circlehook]

I set the floats to what the factory manual called for, new float pins, and gaskets. Cleaned thoroughly and used compressed air tru the air passages. I am stumped

 

[circlehook]

Originally my problem started with the fuel lines deteriorated on the inside and clogged everything I replaced all the hoses and even rebuilt the fuel pump one of the diaphragms had a small hole in it also

 

[circlehook]

And a new raycore water/filter. I am at the end of my rope with this engine

 

[Faztbullet]

Sounds like pressure valve on block is not bleeding off oil tank. This causes oil to be pushed thru oil pump and into fuel line making mixture extremly rich. Also seen it push oil seal out of pump flooding port side cylinder with oil

 

[circlehook]

The oil pump has been taken off and now running on premix and it’s brand new high test and the correct amount of oil 50:1

 

[circlehook]

I am going to try a new set of spark plugs hopefully there just not firing perfect they are a few years old but still look good there those with no electro more like a complete circle

 

[Faztbullet]

It gonna smoke with premix and if recirc valves are clogged even a lil more till the reeds clear out. Clean the ricirc valves and check fuel pump diaphram just for giggles

 

[circlehook]

Thanks will do.
Bob

 

[circlehook]

Oh those are the (6) one way valves you check with a vacuum gauge just want to make shur

 

[Faztbullet]

Fire it off and while running pull the hose off nipple with long reach needle nose. It should spray out in a fine mist, if thick or sputters they need clean/replaced

 

[circlehook]

Great so should I also check with the vacuum gauge or is it not necessary

 

[Faztbullet]

IMO not necessary. If it doesn't spray it has a problem