87 Mercury Classic 50 SETTING CARBS

[NGABaldEagle]

I thouroughly cleaned the carbs and she idles high.
Seems that way to me.

It doesnt have a tach.....is that something I can add?

Anyway to test or identify what the rpm's are besides a tachometer?

I want to try and get this thing right and I am really in an area of no knowledge.

Help!!!
What would you do to get the idle down.

1987 classic 50 4 cylinder dual carb
In Mercury book as 45hp cylinder because of serial number 0B160042.

 

[WillyBWright]

Re: 87 Mercury Classic 50 SETTING CARBS

American outboard idle is set via timing. The throttle butterflies have holes in them to set a fixed idle air flow. One of the many strange quirks about outboard motors that you will see nowhere else. Make sure both carbs are fully closing at idle. Classic Fifty had Hp measured at the propshaft, the older cousins were measured at the crankshaft. A bit of Hp is lost in the gearcase. That's where the difference comes in.

 

[NGABaldEagle]

Re: 87 Mercury Classic 50 SETTING CARBS

The automatic choke is broken and should be here in the next few days.
I am fully aware its an electro mechanical device in that the choke solenoid actuated the plunger that pulls it up vertically and the plunger linkage is connected to the same lever as the manual choke.

Are you saying that the floats should be closed for idle?

I have no idea what has been done to this boat as I just got it.

Perhaps I should close the idle mixture screws all the way down and backout 1.5 turns on both as a starting point.

I dont know how to operate a timing light or any of that stuff.

My brother knows how to do it for automobiles so does that mean he likely can do it for this outboard especially since I have the book showing the degrees?

I plan to go and put it in the water to make all of these adjustments.

I seems to idle very high but maybe its because the carbs are all cleaned out.

I really dont know and I am just speculating.

Help please.

 

[WillyBWright]

Re: 87 Mercury Classic 50 SETTING CARBS

The throttle butterflies are the flat round plates that open and close in the throat of the carburetor to allow more or less air to pass into the engine. It will also idle up to 200 more rpm when run on a hose with no exhaust backpressire from being in the water. Once you put it in the water, you'll notice that it'll slow down significantly if things are in proper adjustment. Usual idle jet settings are in the neighborhood of one turn out. When adjusting, don't adjust for the smoothest idle. They need to be about 1/4 turn more open than that or your motor will bog on acceleration and die. Set both needles the same. Start at one turn out and adjust each by 1/8 turn til you get the right mixture. You don't want one set at 3/4 and the other at 1 1/4 for instance.

 

[NGABaldEagle]

Re: 87 Mercury Classic 50 SETTING CARBS

Ahhhhhhh!

No back pressure will idle the engine up.

Thats key information and I speculated that being in the water was the right thing to do as well as the book said do it in the water but not why.

Back pressure is critical here.

on the auto choke at the key the butterfly valves are closed (dual carbs)
when the key is pressed in.
When it is released I am assuming the butterfly vales open back up.

Perhaps I am wrong and it works like a car and gradually opens back up as the engine warms.

 

[NGABaldEagle]

Re: 87 Mercury Classic 50 SETTING CARBS

Are you talking about the other butterfly valve in the back of the carb?
Make sure the linkage to is is set to full closed at idle?

 

[WillyBWright]

Re: 87 Mercury Classic 50 SETTING CARBS

The throttle butterflies are metal (probably brass) plates toward the back of the carbs that twist with the throttle. The choke flaps are black plastic at the front of the carb that flop down and up. There is no automatic choke. Push the button, it chokes. Let go, no choke.

 

[NGABaldEagle]

Re: 87 Mercury Classic 50 SETTING CARBS

Ok.
press the choke at the key swith and it closes the butterfly valves on the carb.
Release the key and release the choke.
Got it.

Going to the lake in a few hours.

I have some work to do this morning and early afternoon....then of to the lake for trial runs and carb adjustment.

Thanks!