mercruiser 3.0L carb

[sti1471]

OK, So I have a 1986 Mercruiser 3.0L engine with an MC-1 outdrive.

I took the Carb off the engine to replace the gasket and clean the carb up a bit. I have never noticed before but after I installed it back on the engine I noticed a possible issue.

I have the carb setup how it was when it came off the boat (95% sure). with the engine turned off, when I move the control lever from Neutral to forward gear all the way to forward WOT the linkage on the carb with the idle screw moves as it should. However I noticed that the throttle plate does not open and close when moving the control lever from idle to WOT. if I press down on the spring loaded part at the top of the carb I can manually open and close the throttle plate.

So my question is;

Is the throttle plate supposed to open and close with the engine off when I move the control lever to WOT, or is this done electronically when the engine is running?

The idle cam on my carb is screwed into the body of the carb which the rod attaches too that opens the throttle plate. However there is a little "leg" on the idle cam that I am not sure if it is supposed to hook onto something so what when the linkage moves it pushes/rotates the idle cam thus opening the throttle plate.

Any help would be great. Thanks in advance

 

[Don S]

Re: mercruiser 3.0L carb

Are you talking about the throttle plate or the choke plate here. The top one is a choke, you have to open that one and look down into the bottom of the carb to see the throttle plates (2 of them).
The throttle linkage and lever only control the bottom ones.

 

[thumpar]

Re: mercruiser 3.0L carb

I think you are referring to the choke and not the throttle plate. The choke is at the top of the carb. The butterflies for the throttle are that the bottom of the carb.

 

[sti1471]

Re: mercruiser 3.0L carb

I think you are referring to the choke and not the throttle plate. The choke is at the top of the carb. The butterflies for the throttle are that the bottom of the carb.

Yes, Sorry I was not aware of the 2 different plates. I am referring to the choke plate. So the choke plate is not supposed to open and close with the control lever. That is good news to me because I thought the carb had an issue or I hooked it up wrong.

So since the engine is off and cold, the choke plate is closed 100% to begin and I assume this is normal for a a cold engine while it is off, or should the choke plate be open a little bit to allow air in the carb?

 

[Don S]

Re: mercruiser 3.0L carb

So since the engine is off and cold, the choke plate is closed 100% to begin and I assume this is normal for a a cold engine while it is off, or should the choke plate be open a little bit to allow air in the carb?

Yes, it should be closed. As the engine warms up, the choke should move to full open. Usually within 5 minutes or so.