Mercarb Fast Idle Cam

[Monty51]

I'm wondering if anyone else has noticed that the fast idle "cam" on a Mercarb doesn't actually have any eccentricity to it. It's my understanding that the fast idle cam should open the throttle a tad when the choke is closed, then, as the choke heater warms up it should move the cam to it's low mark and close the throttle some. I'm rebuilding a Mercarb and neither the old cam nor the new cam has any eccentricty to it whatsoever. I take a dial caliper to measure from the cam pivot hole to the cam outer edge, and it's a consistent 29/64" all the way.

Has anyone else seen this? I wonder what I'm missing here.

Thanks.

 

[burtonrider11]

I'm wondering if anyone else has noticed that the fast idle "cam" on a Mercarb doesn't actually have any eccentricity to it. It's my understanding that the fast idle cam should open the throttle a tad when the choke is closed, then, as the choke heater warms up it should move the cam to it's low mark and close the throttle some. I'm rebuilding a Mercarb and neither the old cam nor the new cam has any eccentricty to it whatsoever. I take a dial caliper to measure from the cam pivot hole to the cam outer edge, and it's a consistent 29/64" all the way.

Has anyone else seen this? I wonder what I'm missing here.

Thanks.

I can't say that I know a lot about the fast idle cam in the MerCarb. However, it is my basic understanding (I may very well be wrong) is that there really isn't any kind of fast idle on startup - aside from simply pushing the throttle forward. The choke plate is designed to close and then slowly open as it warms.

It seems that alot of people equate a fast idle cam to starting a car where on initial start up it runs at a higher RPM and then slowly backs down. My understanding is that marine applications do not have this feature. Again, I could be way wrong on this, I am no expert.

 

[Fishermark]

burtonrider has it correct. Your carb doesn't have a fast idle cam. When you start your engine with the controller in the neutral only position you can keep the idle speed up till it warms up.

 

[Monty51]

Ok, thanks folks.