Merc Carb 2 barrel rebuild (question the pump rod measurement)

[rhillman75]

1996 Merc Carb 2 barrel with the 3 hole pump rod "lever" for the accelerator pump. The pump rod has always gone in the "middle" hole. My question is about the measurement of the pump rod. The only way I can get the 29mm measurement is to actually bend the rod at the idle cam to where it forces the "lever" up a tad on the accelerator pump. I was always told to just leave the throttle valves closed, make sure the accelerator pump "lever" does not move up or down, and then bend the rod to match both attaching points. Like I said, the only way I can achieve 29mm is to have the accelerator pump "lever" forced up a tad (maybe 1/8 inch higher than the last setup. Merc Carb 3310-806972A 1.

 

[davenph]

Re: Merc Carb 2 barrel rebuild (question the pump rod measurement)

I am rebuilding the Rochester 2-barrel carburetor for my '98 3.0 MerCruiser. I was able to get the 29mm adjustment by positioning the rod in a vice, which enabled me to closely control the amount of bend I was putting in the rod (in the middle of it).

 

[rhillman75]

Re: Merc Carb 2 barrel rebuild (question the pump rod measurement)

I guess my question still remains. If you are adjusting the pump rod arm at the bend section. If the throttle valves are in closed position and the idle screw backed out, should the pump rod be pushing "up" slightly on the accelerator pump lever? In other words, if the rod is out, my pump lever falls to rest point. If I put the rod in and measure the 29mm that it calls for, it takes the pump lever from the rest point and lifts it up about an 1/8 of an inch. Is that normal?

 

[achris]

Re: Merc Carb 2 barrel rebuild (question the pump rod measurement)

.... Is that normal?

I can't say if it's normal for your carb, but I can tell you that I have often had to move the accelerator pump arm in order to get the rod in. As long as it doesn't 'bottom out' on full stroke when you move the throttle shaft to full open, you should be good to go.

 

[rhillman75]

Re: Merc Carb 2 barrel rebuild (question the pump rod measurement)

I can't say if it's normal for your carb, but I can tell you that I have often had to move the accelerator pump arm in order to get the rod in. As long as it doesn't 'bottom out' on full stroke when you move the throttle shaft to full open, you should be good to go.

:clap2: That's the answer I was looking for!!!! I thought it was kind of wierd that on the original rebuild from 3 years ago that the pump arm was at rest even before the rod was removed (wear and tear?) The marina was going to charge me $75.00 just to look at it and verify that the bend was accurate at 29mm. I told them that the throttle valves were closed and I had to move the arm up to get the rod in place for it to hit that 29mm. It is the Merc Carb 2 barrel with the 3 hole arm and I am using the middle hole.

 

[cr2k]

Re: Merc Carb 2 barrel rebuild (question the pump rod measurement)

Adjust the lever for the max stroke and most fuel. You must use the oem spring on the accelerator pump stem. You want the one one that is stiffest or you will have a bog. And Yes sometimes you have to adjust things.

 

[rhillman75]

Re: Merc Carb 2 barrel rebuild (question the pump rod measurement)

Adjust the lever for the max stroke and most fuel. You must use the oem spring on the accelerator pump stem. You want the one one that is stiffest or you will have a bog. And Yes sometimes you have to adjust things.

Okay, so now you have me pondering and wondering...:facepalm: I see in the Merc manual it states of the 3 holes in the lever and that each of them meter the fuel. So if I am understanding you correctly, I can use any of the 3 holes in the lever as long as I get the 29mm reading from the arrestor mounting surface and the throttle valve lever (as long as they are closed). If I have it set at the 2nd hole, what is the gain or loss if I go to another hole as long as I maintain the 29mm reading? And all this time I was just questioning the reason why the pump rod had to put a little lift on the accelerator pump lever to obtain the 29mm that the manual calls for. I was so concerned about the "bottom out" effect from the full throttle position that I went out to the garage and pulled the rod out and manually compared the difference between the accelerator pump lever being full "up" compared to my pump rod setting. Needless to say, at my setting at 29mm, I was okay by at least an 1/8 of an inch. And to this day, maybe I should call it a non-career change and just send it to the marina! :facepalm:

 

[achris]

Re: Merc Carb 2 barrel rebuild (question the pump rod measurement)

The 29mm rod length is it's 'initial' setting, and it needs to stay fixed at that. The different holes in the lever give a different stroke to the acc pump. The hole closest to the pump is the leanest, and WILL cause hesitation on acceleration. The hole furthest from the pump is the richest and the one recommended by Mercury....

HTH,

Chris.....