Mercruiser 470 Choke Issues

[JonRiley56]

Hi,

I have a 470 that is giving me choke problems. It has an electric choke and starts OK, but when it warms up it dies as soon as you give it any gas. I am able to keep it running if I sit back at the motor and feather the butterfly by hand. I have limped back to the dock a couple of times this way.

It seems like the choke isnt sensing when the motor warms up and adjusting appropriately. I have looked at the wiring diagrams in my shop manual but cant seem to find where the choke is picking up its information about how hot the motor is.

Can anyone help me ?

Thanks

jon

 

[Don S]

Re: Mercruiser 470 Choke Issues

Basically, after the choke warms up it should be wide open. What is this "Feathering the butterfly by hand" you are referring to?
If it's open and you have to close it, something is wrong.

Have you checked or do you have a water seperating fuel filter?
Sounds a lot like water in the carb.

 

[JonRiley56]

Re: Mercruiser 470 Choke Issues

Hi Don,

Thanks for the reply ! I do have a water separator on the fuel line. I actually took the flame suppressor off, unhooked the throttle linkage so I could control it by hand, had my son turn the motor over to start it and then I controlled the choke by hand, adjusting the position so the motor will run.

How does the choke know what temperature the motor is at ? I am half tempted to put a manual cable on it if I can figure out how.

The choke body can be twisted to adjust the tension on the spring. Do you know how it should be set when the motor is cold ?

This issue proved to be my nemesis last summer, I really hope I can get it resolved for this season.

jon

 

[Don S]

Re: Mercruiser 470 Choke Issues

To adjust the choke.
Let the boat set overnight. Here is the process I use, and it never fails me.
Just raise the throttle slightly, Now, turn the choke coil so it JUST closes the butterfly. Tighten it down and it should work properly.

Sorry that it's not more complicated than that, but that is all there is to it.
Merc specs (IMHO) are way too tight.

 

[JonRiley56]

Re: Mercruiser 470 Choke Issues

Hi Don,

THanks again. What do you mean by "raise the throttle slightly", I want to make sure I do this right. Also, do you know where the wires that plug into the thing come from ? I should probably make sure that things are hooked up right on the other end................wherever that may be...........

jon

 

[MikDee]

Re: Mercruiser 470 Choke Issues

The wire for the electric choke is just a hot wire (12volts) that comes on with the ignition, heating the element opening the choke butterfly as it gets hot.

 

[Bondo]

Re: Mercruiser 470 Choke Issues

Ayuh,......

By the sounds of your post,.....
It sounds like the Idle Circuit is Plugged,+ Not working properly,+ You're trying to Fix it by blaming the Choke.......
It Sounds like your Carb needs to be Rebuilt,+ Cleaned.......

The Choke starts coming Off as soon as the key is turned to the "On" position,......
It doesn't Sense heat in any way.....And it's Not supposed too......

 

[JonRiley56]

Re: Mercruiser 470 Choke Issues

Hi,

Thanks for the addtional information ! I played with the position of the choke body with the motor cold to get it to run right. I then have problems with the motor when it gets hot. It seems fine till it heats up.

Do you think I was trying to compensate for the "idle circuit" or a carb problem with the choke when the engine was cold ?

If so, what is the plan from here ? Don suggested opening the throttle just slightly with a cold motor and turning the choke body till the butterfly just closes. I can do that and hopefully get the choke body to where it should be.

Can you elaborate on the "idle circuit", are you talking about the fu,e flow in the carb at idle ? Sorry about all the questions, I am kind of new at this. The kids love the boat and I want to make sure we get a lot of time on it this summer.

jon

 

[Bondo]

Re: Mercruiser 470 Choke Issues

Ayuh,....

A Carb has various passages for the fuel to flow thru,....
Each is called upon at various times by either vacuum signals, or mechanical controls,....
If the Idle Circuit is Plugged or Restricted by Crud,..... It needs to be Cleaned out,+ a Rebuild Kit is the easiest way to do it.....
Many times the Crud,+ Corrosion is just Too Bad,+ the carb needs to be Replaced.....

Try setting the Choke as explained by Don,....... If that doesn't work,.....
Try Rebuilding your Carb,......If that doesn't work,.....
Buy another Carb......

 

[JonRiley56]

Re: Mercruiser 470 Choke Issues

Thanks ! I will do both, now is the time to get into the carb. Any suggestions on where to buy a rebuild kit ?

jon

 

[Bondo]

Re: Mercruiser 470 Choke Issues

Ayuh,.....

I gotta believe that a short Search right here at iboats.com will find the right Sierra replacement parts for your motor,......

 

[JonRiley56]

Re: Mercruiser 470 Choke Issues

Yeah, no kidding............I felt kinda stupid after I asked. I found the right section on the web site. I will get the number of my carb and order the rebuild kit. Is there anything in particular I have to watch out for when i do this ?

thanks

jon

 

[Coors]

Re: Mercruiser 470 Choke Issues

Make sure you soak it in QUALITY cleaner, and blow all passages out with an air compressor.