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Thread: Holley 2300 stalls under quick throttle response/load.

  1. #1

    Default Holley 2300 stalls under quick throttle response/load.

    Marine Ford 302. I've had issues trying to troubleshoot this on boat forums. Now that I think I have narrowed the issue to the carburetor, I have gone to the experts! My issue is that my engine will stall with quick throttle response (in neutral) or if in gear when trying to pull a skier out of the water. We have checked the timing on the boat (BID ignition), and it is set correct at 10o BTDC. The mechanical advance in the distributor seems to be advancing correctly.

    My carb is a Holley 2300 (marine) 490 CFM carburetor. It is currently setup with:
    • 3.5 power valve
    • #71 jets
    • White accelerator pump cam

    The engine manufacturer (OMC) specifications are so someone (previous owner) had moved me away from here:
    • 3.5 power valve
    • #72 jets
    • Orange accelerator pump cam

    I worked on diagnosing the issue, and here is what I tried:

    1) Checked the vacuum on the engine and when the engine starts it goes up to around 17 in/Hg which it on the end of the "good" range for vacuum pressure:

    After it idled for a bit, it ended up settling around 18.5 in/Hg:

    This power valve doesn't follow the generic convention people use for Holley carbs, so we thought we would start there to try things.

    3) We swapped out the power valve (what I think is a 3.5 since the markings are UNREADABLE!) for a power valve (PV) plug. That totally takes the power valve out of the equation. The engine did NOT like that, and it ran like crap at idle and barely could stay running. Stalled when you tried to give it even the smallest bit of throttle. This was not the answer.
    Result: Going to PV plug did not help at all (made it worse).

    4) My uncle had a 6.5 PV from his car so we decided to give that a try. You could feel the physical difference in the springs stiffness between the 3.5 and the 6.5 (with the 6.5 being much stiffer). We swapped that in and then started the engine. At first, it seemed to idle rough (looping?) but we adjusted the idle speed and that seemed to smooth it out. At that point, I tried hitting the throttle hard and it worked! It was able to rev really fast and get there quickly, where it would have stalled before. We even noticed that maybe the jet spray looked more uniform?
    Result: Going to a 6.5 PV seems to solve stalling at quick throttle issue (but made it not idle well).

    4) Then we went then to try to get the idle speed to be within spec and get the engine to run smooth at idle, it was running very lumpy/surging. We put the idle mixture screws to the seat and then backed them both off to 1 turn off the seat (manual spec). The engine did not run better, and we could not get the engine speed to the spec 550-650 RPM without stalling. We then played with the screws between 0 turns and 2.5 turns out, and it seemed to be the best at almost seated (1/4 turn?). What was more strange, was that it didn't seem to make a difference in how it idled from 1 turn to 2.5 those screws weren't doing anything?
    Result: Couldn't get boat to idle at speed and smoothly by adjusting idle screws with 6.5 PV.

    So where do I go now? Our thought was to get the carb back to stock as close as possible, since it doesn't like to idle anymore and that is no good. It has currently #71 jets and the spec is 75 so I was going to purchase those and swap those in when I put the 3.5 PV back in. If that doesn't work what would I try next? A 8.5 PV? (18 in/Hg÷2=9) .

    Sorry for the long post. I just wanted to give all the information upfront that I had. Thanks!
    Last edited by tymorrissette; 06-02-2014 at 10:41 AM.

  2. #2
    Join Date
    Dec 2009


    Quote Originally Posted by tymorrissette View Post
    We then played with the screws between 0 turns and 2.5 turns out, and it seemed to be the best at almost seated (1/4 turn?). What was more strange, was that it didn't seem to make a difference in how it idled from 1 turn to 2.5 those screws weren't doing anything?
    A blown power valve (although very rare), can also render the idle mixture screws ineffective.
    There's a power valve testing procedure in this link, if you think yours is defective: (End of page, at left.) (Additional Information)
    May God's grace bless you in the Lord Jesus Christ.
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  3. #3


    Thanks for the response Danny. I don't think it is a blown PV, since while trying to get the idle speed down and playing with the mixture screws, we were able to stall the motor if we went less than a 1/4 turn from close. Any other ideas?

  4. #4
    Join Date
    Jan 2013
    Constantine, MI


    Don't forget to go back to the orange cam. Try cleaning the idle air bleeds and passages; shoot with carb cleaner and low air pressure.
    Last edited by hotstuff; 06-02-2014 at 12:00 PM. Reason: added information

  5. #5


    Do you think it would even make a difference, going from the 71 that's in the carb now, to the 72 that is spec'd out? Is it that sensitive?

  6. #6
    Join Date
    Jan 2013
    Constantine, MI


    I always go 2 sizes, but 1 size = 4-1/2% and jet flow is within a range. So a 71 low side and a 72 high range is a big jump. The only true way to tell, is reading the plugs for the right size jet.

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