How to adjust Mercruiser 3.0 Carburetor

[liusigou]

my Mercruiser is difficult to start if it is cold. How can I adjust my Carbu? thanks you

 

[ESGWheel]

Please provide some more info like engine serial number along with

• Your normal cold start process
• What you do to get it running
• How long has this been going on
• What was done to the engine (maintenance items etc.) between when it started normal to now.
• Other relevant history

It will assist in troubleshooting the issue.

And as the first test, my suggestion is to, with the spark arrestor off and a good flashlight in hand have a helper move the throttle (engine off) from idle to WOT in a smooth stoke while you look down the throat of the carb. You are looking for a stream of gas as the throttle is opened from the accelerator pump akin to as if you were squirting a syringe. Post what you see (a squirt or no squirt). Thanks.

 

[alldodge]

my Mercruiser is difficult to start if it is cold. How can I adjust my Carbu? thanks you

Does this happen each morning/day or is it left for a week or more?

 

[liusigou]

This is a recently purchased used MerCruiser. Even in the summer it was not easy to cold start — I usually had to push the throttle fully open to get it to fire. If I immediately pulled the throttle back, it would often stall, so I had to let it run at high RPM for a while. Once the engine warmed up to around 80°C it would idle normally.

Now with the cooler morning temperatures (around 14°C), the starter motor really struggles to get it going, and after it starts it still needs to stay at high RPM, otherwise it stalls right away.

The carburetor Part No. is 1389-9562.

 

[ESGWheel]

I looked thru some of your other posts and found that this 3.0 is a replacement motor for you. You also has some issues with a noise it was making and even rough idling (link). Did that issue get resolved? The reason I am asking is that while your hard start could be fuel related it could also be many other things, so I am trying to get a sense of the overall health of the motor.

Also, when you do start it and leave it at “high rpm” until 80C > how high is that RPM? 1500? 3000? Or? Thanks.

 

[alldodge]

I'm reading 2 possible issues:
The starter struggles, is the Bat fully charged (12.7V) and our the Bat cables clean and tight?

Throttle at full open, Is the choke closed when cold, is it flooding?

 

[liusigou]

I looked thru some of your other posts and found that this 3.0 is a replacement motor for you. You also has some issues with a noise it was making and even rough idling (link). Did that issue get resolved? The reason I am asking is that while your hard start could be fuel related it could also be many other things, so I am trying to get a sense of the overall health of the motor.

Also, when you do start it and leave it at “high rpm” until 80C > how high is that RPM? 1500? 3000? Or? Thanks.

thank you gor your help. I have replaced the harmonic balance and there is not noise any more. and the maximum speed is about 35 mph with my steel propeller. I will check the RPM when I cold start it.

 

[liusigou]

I'm reading 2 possible issues:
The starter struggles, is the Bat fully charged (12.7V) and our the Bat cables clean and tight?

Throttle at full open, Is the choke closed when cold, is it flooding?

the battery is about 12.91 v. I will check other after I get home

 

[liusigou]

I'm reading 2 possible issues:
The starter struggles, is the Bat fully charged (12.7V) and our the Bat cables clean and tight?

Throttle at full open, Is the choke closed when cold, is it flooding?

The starter should be good. I moved it from my old 2.5 to 3.0

 

[alldodge]

The starter should be good. I moved it from my old 2.5 to 3.0

Not the starter, the starter cables ground and hot