MercCruiser 3.0L Carb Accelator pump problem

[NConroy]

My recently purchased 2000 Bayliner, with MercCruiser 3.0L has a problem with acceleration. Starts OK, but if throttle is pusher quickly it just stalls, in or out of gear. Accelerate slowly and engine runs fine and gets boat onto plane.
I have researched this forum, and others. I have established the carb is a MercCarb, with one idle adjuster on base, the accelerator pump shaft has the 90-degree bend at top and blue washer.
I have stripped down carb, it was in good shape, plenty of fuel in chamber, no waxing, jets clean. I air hosed all jets and air lines, all clean.
My problem is with the accelerator pump. I get no spray of fuel into carb when throttle is pumped. On inspection, the cylinder into which the pump shaft is inserted is way over sized, the washer does not touch sides of barrel, therefore no pumping action, just an up/down movement in the barrel. The barrel is aprox 3" in length, with a slot cut out for aprox two thirds of its
Length.
This would mean there would be no pump action anyway until last third of pump stroke.
Pump cylinder barrel has a light spring inserted into base, this spring mates with bottom of pump shaft.
Is there any website that I can get a exploded view of the innards of this carb?
Can anyone tell if this set-up is correct, and if so where does the pump action come from?
Is it possible the carb was stripped down at an earlier date and reassembled with wrong pump shaft, or is there an insert missing from the pump cylinder barrel?
At this stage I am considering buying a reconditioned carb, you are my last hope of solving this issue?

 

[Fishstick1962]

Re: MercCruiser 3.0L Carb Accelator pump problem

Sounds like you have the wrong accel pump. I have seen blue ones and black ones. The blue is a smaller diameter and will not work in the carbs with a larger hole. It should be snug right at the top of the hole. The blue does'nt make contact until it is 2/3 down in the hole when used in the wrong carb.
Recently, I have recieved two carb kits with the wrong pump in the package.
May have happened to the previous owner.
Anyhow, get the black larger diameter pump and you should be good to go.
They're pretty cheap.
Hope this helps.

 

[NConroy]

Re: MercCruiser 3.0L Carb Accelator pump problem

Thanks fishstick1962
Your observations seem to confirm my suspicions.
I will get the black larger diameter pump as you suggested.
Tried engine yesterday, first time since refitting carb. Was pleased when it started first turn, should run well wen accel. pump is sorted.
Checked timing with srobe, 8 degrees BTC, manual says 2 degrees is the correct setting.
How the previous owner ran this boat is behond me!!!
Anyway, did not intend to have the little rant above.
Can you recomend a reputable supplier (online) for the carb parts?