75hp mercury o/b 2 cycle wont idle, rebuilt carbs, ugh!!

[stang32]

hoping someone can help me with this . my cousins boat, just got it & it was siting for years. i got it running but it would not idle below 1400 rpm. i rebuilt both carbs but still the same issue. sometimes i get it around 800 but it will not last & dies. i am sure if i goosed it & went back to that setting , it would not stay running. i am at a loss on this one., i do not work on outboards in general,all of my work is I/O's but its family.

engine serial # is OA994465

 

[ondarvr]

Check the compression, but most likely the carbs are still dirty.

 

[stang32]

the compression is good, the carbs soaked in lacquer thinner for 2 days & the carbs were blown dry with compressed air.
any other thoughts?

 

[stang32]

it runs real well at 1400rpm.

 

[ondarvr]

Yes, if it doesn't run well at low RPMs, but does at higher RPMs, then the carbs are still suspect. Did you pull out the needles and make sure it was all clean? It's not uncommon to clean the carbs a couple of times before getting all the gunk out.

Have you check for spark at low RPMs?

 

[GA_Boater]

Did you adjust the needles?

 

[stang32]

yes, there is only 1 per carb and i cant get the idle down low enough to feel a difference.
there is spark @ low idle. when it does get down lower. the tach is still reading spark

 

[stang32]

the carb is spotless, i even pulled the 3 caps and made sure there was no crap under them. the needle has been adjusted

 

[wn6ngp]

Maybe there is a vacuum leak due to a damaged gasket for the carbs. I've heard of folks spraying wd40 around the base of the carbs while running, if performance changes then that gives you an idea of where to look. Besides that I wonder if the fuel pump is getting enough fuel there at idle.

 

[jimmbo]

Does it run any different, if you disconnect the plug wires, especially cylinders 1 & 4?

 

[60sboater]

Maybe there is a vacuum leak due to a damaged gasket for the carbs. I've heard of folks spraying wd40 around the base of the carbs while running, if performance changes then that gives you an idea of where to look. Besides that I wonder if the fuel pump is getting enough fuel there at idle.

Do the wd40 test and others you can think of...entire fuel system etc. Does it "sneeze" while running?

 

[stang32]

ok, here's the latest, i disconnected plug wires for cylinders 3 & 4 & i get no spark. i hooked up my timing light to each plug wire & no signal from 3 & 4 confirming the earlier test. so i have now shifted my work from fuel issue to spark. i want to beet my head against a wall, i hate these 2 stroke o/bs.:facepalm::frusty::frusty::frusty::frusty:


a quick search pointed me to a probable stator problem, does that sound right?
how do i test that since stators dont seem to be a cheap fix.
also how do i determine what year this engine is?

oh, 1 more thing, compression test done, all cylinders @ 130psi

engine serial # is OA994465