'94 mercruiser 3.0 rough idle on cold start

[Dylan07]

Boat:
1994 Bayliner Capri 1950
Engine:
1994 Mercruiser 3.0
S/N: 0F176013
When it first starts it runs really rough like its missing. If I give it gas it takes a couple seconds to run good. Then it idles at roughly 1200rpms. Not sure what the problem is.
The high idle may be adjustable. Does my choke look right? Should it smoke like that on cold start? I'm guessing it must be running rich? Am I missing any parts, besides the return spring?
Video included.

Bondo or Don will surely help me out, thanks guys!

 

[alldodge]

The choke looks to be operating correctly, starts with an 1/8 gap and opens up after running.

Carb appears to be running rich but before getting into that, suggest doing a compression test and see what the plugs look like. Need to adjust the idle down some but the idle is set in gear and on the water between 650-700 rpm.

Your reving the motor so high you may have damaged the impeller. Rpms should not exceed 1800 rpm.

 

[enginesilo]

To be honest, it doesn't sound all that bad, and if that was a cold start (Meaning you hadn't run it in days beforehand) that was a smooth start. My 2005 3.0L takes 2 pumps to prime it and then it sometimes starts and shuts down, then starts and runs good. On a warm start it will fire right up without any pumping of the throttle like yours did. Keep in mind these engines are old technology and carburetors can sometimes be a bit quirky.

The idle adjusts very easily with a small set screw you can find on the carb. I have mine idling around 700rpm's right now, but I used to have it down to 500 but it was just too low. Set it while in the water. If too high shifting will sound harsh so set it around that 700rpm range and it should be good.

You are definitely revving that engine a bit too much while on the muffs. I typically try to run it under 2000rpm's when on the hose.

PS, sadly Don has passed a while ago so he is no longer with us, but Bondo, All Dodge, and a few other Merc Ninja's are in this forum and very helpful, they all rock!

 

[stonyloam]

Looks and sounds fine to me as a matter of fact I think it started great (started without pumping the throttle). All carbureted boats will run a little rich and smoke until the choke opens. With the engine open to the air you can start it without the flame arrestor in place to watch the choke open, it looks like it is operating as it should. Adjust the throttle with the throttle stop screw like the other guys said, and you can adjust the throttle mixture screw on the carb base to smooth it out. I kind of cringed a bit when you revved it up, not good. I think I know why you think it is not starting well, you sound like a young guy that has always driven a fuel injected car which start almost instantly. Old timey carbed engines need a little bit of cranking to get them going .

 

[KJM]

I agree with comments above. Sounded pretty good to me and started easily! I also cringed when the engine revved up so high, I wouldn't do that to my car, let alone a boat on a hose.

 

[Bondo]

Looks and sounds fine to me as a matter of fact I think it started great (started without pumping the throttle).

Ayuh,.... Agreed,.... Starts better than my 4.3l, Cold,.....

PS, sadly Don has passed a while ago so he is no longer with us,

Ayuh,.... Just over 3 years ago now,.... seems like yesterday,......

 

[Dylan07]

To be honest, it doesn't sound all that bad, and if that was a cold start (Meaning you hadn't run it in days beforehand) that was a smooth start. My 2005 3.0L takes 2 pumps to prime it and then it sometimes starts and shuts down, then starts and runs good. On a warm start it will fire right up without any pumping of the throttle like yours did. Keep in mind these engines are old technology and carburetors can sometimes be a bit quirky.

The idle adjusts very easily with a small set screw you can find on the carb. I have mine idling around 700rpm's right now, but I used to have it down to 500 but it was just too low. Set it while in the water. If too high shifting will sound harsh so set it around that 700rpm range and it should be good.

You are definitely revving that engine a bit too much while on the muffs. I typically try to run it under 2000rpm's when on the hose.

I did start it the day before that, it was about 24 hours... I figured that's a cold start?
I have tried the idle mixture screw and the throttle screw, and I can not get it to idle below 1000rpm's
Was that revving too much? I am highly confident that it is perfectly fine for car engines, but I suppose the boat would have a hard time getting enough water through a water hose?

PS, sadly Don has passed a while ago so he is no longer with us, but Bondo, All Dodge, and a few other Merc Ninja's are in this forum and very helpful, they all rock!

Damn! I have seen how helpful he was on here, and no disrespect to the other helpful people on here. I have just noticed Bondo and Don help almost every post I have read.

 

[s.hadley81]

Those trim ram nuts on the drive done look right, just my .02

 

[stonyloam]

Check to see if the throttle idle stop screw is actually contacting the cam. It looks like it is not. If you need to push it down to decrease the idle see if you can adjust the cable.

 

[alldodge]

With the idle screw backed out to where its not touching, and if you cannot push the butterfly on the carb closed enough to slow the idle down, I think the throttle plate is bent or binding.

There are screws holding the throttle plates on the shaft, remove the carb and see if it/they are centered.

 

[Dylan07]

The throttle stop screw doesn't touch the cam, I will try adjusting the throttle cable. Also, I wanted to ask if this could be a timing issue? It runs great at higher rpm's but no matter what adjustments I make on the carb it runs really rough/stalls before I can get it to idle rpms.What is the timing on this ngine? I have read 2 degrees ATD, 1 degree BTD, i don't know....

 

[Dylan07]

Well, crap.... I broke the idle mixture screw. I thought it had more to go because it was running fine and high still. I thought the resistance was just paint on the screw. How do I get this out. And may as well rebuild the carburetor?

 

[alldodge]

You might be able to get it out with a left handed drill bit, and then maybe an easy-out, but I would suggest getting another carb. This one has some real issues, and it would be best to start fresh.

From your vid at 51 seconds in it appears you have the Delco EST ignition, so your timing should be 1 BTDC as indicated in the pic below