Lumpy idle after carb rebuild | Holley 2300 | Volvo Penta 3.0 GS

[baker556]

Hi all,

Last year out on the boat always had trouble starting would need multiple cranks at WOT! From research, it was time for a carb rebuild for this season.

Just a note last year had a change of oil, sparks full service etc.

On completing the rebuild of my Holley 2300 for Volvo Penta 3.0 GS on SX outdrive year 2003, Glastron Sx175 (250 hours.) I could not get her to fire at all until holding down WOT for a LONG time waiting to crank. After initial fire she did fire again but still took time to crank this time with choke wide open (air temp circa 18 degrees).

From reading and watching videos on how-to rebuild the Holley carb I thought this was straight forward and without problems, on trying to fine tune the carb once the engine had started, I still had issues with extremely lumpy idle, turning the air/fuel mixture screws had little affect on providing smooth idle.

Looking back through pictures the power valve looks to be ever so slightly different in the pictures (see photos) - would this have major affects on lumpy idle?

I'm also having trouble understanding how to set the float height without a sight hole, any thoughts here?

Overall the boat is running very rich with a sooty exhaust, again see photos of outdrive and video.

The kit was purchased from here and is recommended for Holley 2300 carbs:

Carb Rebuild Kit for Holley 2BBL, Volvo Penta, OMC, 4.3L, 5.0L, 5.7L Replaces 21533400, 3854020

Replaces Volvo Penta 3854020

repowermarine.com

Please see attached video and photos.

If you guys can provide any thoughts into this, it would be appreciated.


View attachment VID_20230730_165709.mp4

 

[dubs283]

Did you replace the power valve and the gasket?

 

[ta79pr]

I swear I hear a vacuum leak. Idle needle jet gaskets good?

 

[baker556]

Did you replace the power valve and the gasket?

Yes replaced, with new gasket, thanks will double check.

 

[baker556]

I swear I hear a vacuum leak. Idle needle jet gaskets good?

Hmm, will listen again, jet gasket done up snug but did leak petrol originally.

 

[baker556]

Any one have ideas as to why it takes so long to fire after cranking? Could it be a old/worn spring for the accelerator pump?

 

[Scott06]

Any one have ideas as to why it takes so long to fire after cranking? Could it be a old/worn spring for the accelerator pump?

Is the choke closing. Did this change after rebuild or was it an issue prior- could be ignition related

I think the float level is just parallel to bowl top basically level

How did you clean the carb components during rebuild

 

[baker556]

Is the choke closing. Did this change after rebuild or was it an issue prior- could be ignition related

I think the float level is just parallel to bowl top basically level

How did you clean the carb components during rebuild

Carb cleaner and a rag.

Choke is closing as the engine warms, fully closed when cold, but either or starting is difficult.

 

[Scott Danforth]

Did you chase every passage with a piece of fishing line to make sure they are open? Is the squirter nozzle check valve free to operate?

 

[Scott06]

Carb cleaner and a rag.

Choke is closing as the engine warms, fully closed when cold, but either or starting is difficult.

If you didnt get the passages clean by chemical and mechanical means, and blown out with compressed air that is likely the reason for continued issues.

I have had really good luck with a small HF ultrasonic cleaner have used both carb cleaner and simple green ( to keep from removing paint on carb) successfully.

You might dump a little gas down the carb prior to cold start see if it fires right up. I have found that if the ignition system is in good shape the slightest wiff of gas and it will fire quickly. If this improves the start, go back into the carb and clean it again.

Who made the kit you used, there are a lot of junk parts out there would make sure needle seat and float are working ok

 

[baker556]

Did you chase every passage with a piece of fishing line to make sure they are open? Is the squirter nozzle check valve free to operate?

Nope, just cleaned with carb cleaner - I'll look at this again over the weekend.

Any ideas on setting the float height and where to take a vacuum feed from?

 

[baker556]

If you didnt get the passages clean by chemical and mechanical means, and blown out with compressed air that is likely the reason for continued issues.

I have had really good luck with a small HF ultrasonic cleaner have used both carb cleaner and simple green ( to keep from removing paint on carb) successfully.

You might dump a little gas down the carb prior to cold start see if it fires right up. I have found that if the ignition system is in good shape the slightest wiff of gas and it will fire quickly. If this improves the start, go back into the carb and clean it again.

Who made the kit you used, there are a lot of junk parts out there would make sure needle seat and float are working ok

Sorry I meant the choke is closed on cold start and open on warm start.

Thanks, I will try this however why would it suddenly be lumpy? When last season it wasn't lumpy just hard to start?

 

[Scott Danforth]

no need for vacuum feed if you have a tach and an unlit propane torch

 

[baker556]

Is the power valve an issue as per picture they're ever so slightly different.

 

[baker556]

no need for vacuum feed if you have a tach and an unlit propane torch

I don't have the propane torch =)

 

[Scott Danforth]

rule of thumb.... your starting point on a holley carb is always 3/4 turn out from seated. 99% of the carbs will be between 3/4 and 1 turn out with most in the 3/4-7/8 turn range

 

[baker556]

rule of thumb.... your starting point on a holley carb is always 3/4 turn out from seated. 99% of the carbs will be between 3/4 and 1 turn out with most in the 3/4-7/8 turn range

Cheers Scott, will try this setup.
Do you know where about the best place would be to plug into a vacuum gauge on this type of carb?

 

[Scott Danforth]

Cheers Scott, will try this setup.
Do you know where about the best place would be to plug into a vacuum gauge on this type of carb?

There is no place on a marine carb to plug in a vacuum gauge

 

[baker556]

There is no place on a marine carb to plug in a vacuum gauge

How do others test this then? There is various youtubes showing this on other holley marine carbs?
Could I tap into any vacuum hose?

 

[Scott06]

How do others test this then? There is various youtubes showing this on other holley marine carbs?
Could I tap into any vacuum hose?

There may be a vacuum fitting plugged on manifold

There is vacuum supplied through a small tube for the choke pull off

Prob can put your gauge on there and just force the choke open

Can also just tune it by ear or rpm when you go way lean and way rich it will stumble In Between these two extremes is best idle usually