Running lean - Clean the jet?

All good. Took apart and found a small tiny piece of old gasket clogging the acc hole to or from the metering block. Put back together, adjusted the idle screws and it rocks now. The 3k limit was my brainfart end of day not thinking. The throttle limits this when revving the engine.

[QUOTE=gun-driver] Very good write up on adjustments.
This got me thinking he could have a small vacuum leak causing the lean condition.
QUOTE]

Vacuum leak would make it run like crap. This is just an off idle stumble.

tommer12 wrote: Just to make you all even crazier.    The accelerator pump is adjusted for it's largest shot of fuel. And the fact that you can almost completely close the choke with no adverse effect on the way it runs indicates a lean running condition.

What do you mean by adjusted for the largest shot of fuel? What accelerator pump cam are you using? Which hole in cam? What size accelerator pump discharge nozzle? What size accelerator pump? If you really had it set for the largest shot of fuel on a fairly stock engine you'd be getting a terrible rich bog and black smoke every time you punch it... Might even stall depending on displacement, cam, prop/gearing and if you have a double pumper.

What you described initially is a lean stumble, indicating you need more accelerator pump shot. First step is to make sure the discharge nozzles are clean/clear and shooting vigorously straight at the boosters, not dribbling or only shooting one side, etc. Adjust accelerator pump arm just a little tighter than zero lash (I believe you have done this already).

If you can close the choke on a warm engine idling and it runs better then you need to adjust the idle mixture... If still lean then you need to rebuild teh carb as your idle fuel passages in the metering block are likely gummed up and restricted.

Turn idle mixture screws all the way in, lightly seat (do not tighten or you will damage the screw and/or metering block). Set each out 2.5 turns. Start engine at operating temp and if idle is rough, turn both out .5 turns at a time until idle is smooth. Adjust throttle stop screw for desired idle RPM (around 750 in neutral should be good). Turn idle mixture screw in slowly, 1/8 to 1/4 turn at a time until engine stumbles (RPM drops), turn screw out 1/4 turn. Repeat for other idle mixture screw. Now check your RPM and adjust the throttle stop screw if RPM has changed from your initial setting. Re-adjust the idle mixture screws again, after each time you change throttle stop screw position. Basically you are adjusting for highest idle RPM/highest vacuum at the throttle stop setting that gives you the desired idle RPM. It is preferable to do this at idle in gear but not necessary, results should be very close. Fine tune in gear if your idle in gear is not as nice as you'd like.

While you're at it set your initial timing and advance curve. A slow or non functional advance will give the same results as a lean stumble on acceleration. It is common on marine distributors for the advance mechanism to become rusty and sticky. Disassemble and clean/lubricate if required.

Increase RPM and watch the timing as you do so. Should be a fairly smooth curve to full timing in around 2500-3000 RPM. Total timing should be around 32*-38*, depending on heads/cam/etc. will dictate where it performs best. 10* initial is pretty safe but if it'll take more initial without detonating or being hard to start (kicking back, slow crank) you can get a little more low RPM performance and a better hole shot. I'm talking like 12*-14* max, since it is a boat and under heavy load all the time. Just be sure you don't have detonation as it'll crack pistons and ring lands. Also make sure you're not getting crazy with total timing, 38* is a lot, 40 or more is just plain too much. If you're not experienced with tuning and listening for detonation, don't push your luck and a curve starting at 10* running up to low or mid 30's will be fine.

backfoot100 wrote: I would not adjust it like Holley says. I believe they want .015" (or something like that) clearance between the pump arm and diaphram. I'm just trying to remember right off the top of my head but could be wrong on that clearance.

The Holley stuff isnt clear about that adjustment.. the .015 is when the clearance you should be able to measure while holding the throttle at WOT. IE not bottoming out the pump by a minimum of .015. You have certainly been achieving perfectly acceptable results by taking out all the slop and having a slight preload at the throttle closed position.

Certainly you are correct in saying that .015 clearance with the throttle closed would lead to a stumble.

Yes, mines on the the trailer at the ramp, I would think Pete has the sense to lower his to the water in the slip. My neighborhood ramp is cantilevered over a 20 ft drop, I can get on the throttle quite a bit if I want without worrying about tearing up the end.

tommer12 wrote:    In the water under load is actually better, but on the trailer in gear will be ok.   Just dont keep it in gear long.

My err. I assume everyone has their boat in the water!
I'm not ok with this trailer adjustments

The load of the water is very important to the quality of the idle adjustment.

And don't risk the cutlass bearing turning it dry.

Its already adjusted exactly how Holley specs are for it. When I say sloppy, when you move the throttle back and forth, the pressure at full with a feeler gauge, seems sloppy, not tight. Im guessing the diaphram has had seen better days because of the friggin ethanol in California gas.

By the time I buy an ACC pump, and if my gaskets break, I might as well just buy the kit.

?, the motor doesn't know or care if it moving, it's just turning the prop like its supposed to.

I adjust my idle circuit in the boat house slip and dredge some of the sand out at the same time!

GottaSki wrote: Are you certain you adjusted the idle circuit IN GEAR? this is critical. If you did it in nuetral, you will set it too lean and pretty much induce the hesitation you are trying to eliminate.

Wondering, does it make any difference if the boat is moving in gear, or tied to a stationary object that keeps it from moving?

Accelerator pump arm has zero slop without bottoming out the pump diaphram? Getting a good squirter shot at the slightest touch of the throttle?

Pete's right. You may just need a little tweaking on the accelerator pump.
You should do a little more idle circuit tuning also. Get it warmed up and put it in gear idling and make sure the idle mixture screws are set to give you highest RPM or highest vacuum if you have a vacuum gauge.

Get those two things dialed in and I'll bet your stumble disappears.
Your jets are fine.

Drop the hammer and it hesitates which make me thinks the jets are dirty, not getting enough fuel. But if I easy into the RPMs, no issues. Its for sure a fuel delivery problem. Idles great, no top end issues.   Maybe lean is not the correct term, but we think the jets are dirty.   Last rebuild was in 2006.

Im running a little lean on the carb and I think my jets are dirty.   Is there a good document out on the internet how to clean or replace my holley jets?    It looks like just simply taking off the bowl and unscrewing the jets. Get a new blue gasket, jets and put it back together.