3.0 L Merc carb question

[rmcel123]

I have been checking things out with my new boat. 3.0 L merc engine and carb in it. Cleaned the in carb filter, had some crap in it. Has the bogging issue others have talked about and will probably adjust accelerator pump linkage to improve that. I noticed that the large butterfly plate at the top of the carb is loose. The 2 screws are in but need to be tightened with some locktite. I can't figure out how to turn the plate up to get at them.

I tried throttle positions in gear and in neutral. I played with the linkage to see if I could get it to flip. I even put 12V on the choke to see if it would flip. Nothing. I haven't done any of these with the key on yet, all with no power to the boat.

Anyone know how to flip this plate up?

Thanks in advance

Dave

 

[Bondo]

Re: 3.0 L Merc carb question

I have been checking things out with my new boat. 3.0 L merc engine and carb in it. Cleaned the in carb filter, had some crap in it. Has the bogging issue others have talked about and will probably adjust accelerator pump linkage to improve that. I noticed that the large butterfly plate at the top of the carb is loose. The 2 screws are in but need to be tightened with some locktite. I can't figure out how to turn the plate up to get at them.

I tried throttle positions in gear and in neutral. I played with the linkage to see if I could get it to flip. I even put 12V on the choke to see if it would flip. Nothing. I haven't done any of these with the key on yet, all with no power to the boat.

Anyone know how to flip this plate up?

Thanks in advance

Dave

Ayuh,.... Welcome Aboard Dave,...

Are you tryin' to close the choke, or open it,..??

Which carb ya got,..??

 

[rmcel123]

Re: 3.0 L Merc carb question

I am trying to open it I think. It is closed by default isn't it or it should be I think. The butterfly plate is vertical right now and I can't access the screws because of that. I want the plate to go horizontal.

I have the 43mm Mercarb 2bbl units. Cleaned the fuel filter in the carb, lubed every linkage, picking up my new gas tank sending unit (other one is plastic and pooched!) tomorrow and will have it ready for saturday! Just want to tighten these screws.

I am going to turn everything on tomorrow after installing the sending unit and see if powered up will cause the butterfly to open, or close. I think that's the only way it will work, simulate a start with the kill switch off of course. Just trying to confirm this with anyone that has had experience.

Dave

 

[kd7isf]

Re: 3.0 L Merc carb question

that plate is called the choke butter fly.

It should be closed under spring pressure until 12v is applied to it. Then it should slowly open.

WARNING!!!!!! DO NOT ATTEMPT TO START THE ENGINE IF THE LITTLE SCREWS HOLDING THE BUTTERFLY TO THE CHOKE SHAFT ARE LOOSE!!!!!!

If those screws fall out, they can be injested into the engine and cause severe engine damage!!!!

Do NOT force it past the straight up and down position -- you will damage it.

You have to take the top cover (called the airhorn) off to get to the screw heads on those. You will need an air horn gasket since you will most likely destroy the one thats there when you open it.

Just unscrew the loose screw(s) and coat them with locktite (I'd even go so far as to use red locktite on those screws) and then screw them back in.

Warning, be carful not to disturb the float and make sure not to let any little dust, dirt, grit, or grime get in there while you have the top off........

Hope this helps

 

[rmcel123]

Re: 3.0 L Merc carb question

Thanks for the advice. I knew that they shouldn't be loose but somehow were. I started up the motor in the driveway and I still could not get the choke to move. The boat starts great and runs fine so everything seems to be working. The air horn wouldn't move at all. I finally put a rag inside the carb and slowly backed the screws out with needle nose. Once out far enough, put loctite on screw and on back of screw hole to hopefully get it in there. Tightened it all up and seems good to go. I will watch it over the summer. My plan is to do a carb rebuild next winter so I will fix it properly then.

Thanks again for all help.

Dave