IDLE Adjustment

zippy83

Chief Petty Officer
Joined
Jan 1, 2013
Messages
491
Hi All,

I was wondering if someone can help me figure out how to adjust my idle. I have a very old 1973 Mercury 2 Stroke 50HP outboard. It has been running like a champ for the past 47 years but recently it has been stalling when I turn it on and when it sits in idle for more then 2 minutes. When I turn it on (cold start) I was told to always pull the handle to give it more gass and it turns on just fine but when I move the handle back and it starts idling you can hear that it's going to shut off. It is barely running. Also when I put it in gear and if I dont immediately give it throttle it stalls. So If I just put it in gear it will stall. When I put it in gear and immediately give it some throttle it runs. When in gear it runs perfect I see or hear no issues it's just when It's idling and when you put it in gear that it stalls.

Now I have noticed that when It has been running in gear and you put it in Neutal it stays on but it is barely running , like you can hear it struggling. Then when I put it in gear same thing runs but it is struggling to stay on.

I have attached a few Pics of the outboard. The one item that is circled is a part of the outboard that moves back when I pull up on the cold start handle. There is also a screw in front of it and I was wondering if that is the idle adjustor?

I know it's an old motor but this thing has been great. I get 32 mp/h max on my 1650 deep V Lowe, and I have had no issues since I got it 10 years ago. I hope that this is not something serious..

Thanks in advance
Zipp
 

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racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
37,846
Start the trouble shooting with a compression test.-----Are you putting a new water pump impeller in about every 5 years ?
 

zippy83

Chief Petty Officer
Joined
Jan 1, 2013
Messages
491
Start the trouble shooting with a compression test.-----Are you putting a new water pump impeller in about every 5 years ?

Current water pump Impaler is 3 years old. Looking at the water that comes out when on idle is a bit spoty but with a bit of throttle seems to have a good flow. If there was a compression issue wouldn't I notice performance issues under load?
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
37,846
Internal engine issues cause idling problems / stalling .-----Inspection and trouble shooting cost no coins !!
 

zippy83

Chief Petty Officer
Joined
Jan 1, 2013
Messages
491
Ok what is the easiest way to do a compression test and what should I be looking for when doing one? I was watching a video on youtube on how to do a compression test and seems pretty simple. A lot of guys keep saying to ground the plugs when removed but I'm not sure what they mean exactly with that statement.

Also some say open up the throttle when cranking others say dont do it it will cause issues..
 
Last edited:

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,739
When was the last time the carbs were cleaned ?
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
37,846
On a 2 stroke like that there is NO NEED to open the throttle for a compression test !!
 

Mark ofs

Petty Officer 3rd Class
Joined
Aug 2, 2020
Messages
75
Ok what is the easiest way to do a compression test and what should I be looking for when doing one? I was watching a video on youtube on how to do a compression test and seems pretty simple. A lot of guys keep saying to ground the plugs when removed but I'm not sure what they mean exactly with that statement.

Also some say open up the throttle when cranking others say dont do it it will cause issues..
I know this is late, but to ground the sparkplug, I made a "jumper" cable using alligator clips, attached one clip to the spark plug base, the other to a good ground on the outboard.
 

racerone

Supreme Mariner
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Dec 28, 2013
Messages
37,846
Post the compression numbers.----No need to open throttle plates for this testing.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,861
Mercs in good condition do that all the time, when they are out of tune. However, it doesn't mean your motor is in good condition.

try some fresh 50::1 fuel mixture. If that doesn't get it, you will need to clean the carbs and rebuild them with new floats, gaskets and inlet needles and seats. It is best to do an link and synch. A Mercury Service manual is best to help with L&S.

Carb idle mixture is key. It must be rich enough to allow smooth acceleration, yet lean enough to allow good idle.
 
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