Is there any problem with manually locking out the 2ndary air valves and making a few acceleration runs?

I've been chasing a small problem with my Edelbrock 4 bbl 600 cfm carb on my boat and I think I narrowed it down to the 2ndary's coming on too fast, creating a lean spot. From a dead stop, hammer the throttle and the boat starts off very well, but within about 5 seconds you can feel it lose power for about another 5 seconds. If you hammer it then immediately back off to 90% throttle, it's perfect. No lean spot. No loss of power. This seems to be the throttle thresshold just before the 2ndaries open up.

Marine 1409 carb. 305 vortec motor. Edelbrock performer intake, mild cam upgrade. Relatively new parts.

I've been through the manual and searched many threads here. I've been up/down the rich/lean tuning and am currently (back to) normal metering on the primaries and +2 jets on the 2ndaries (per info on this board via Edelbrock addressing what appears to be exactly my issue).

Timing is currently at 32 deg at 3000 rpm's. No performance changes when I had it at 36 degrees.

A general tune up (cap/rotor/plugs/wires) has been done-no changes.

I've adjusted the accelerator pump and it's working, but the carb just isn't transitioning very well.

I currently have the 2ndary air valve locked out with a thin strip of aluminum that is fastened to the primary metering spring cap screw and I only want to run a few acceleration runs to see if the lean spot goes away. No wide open throttle pass, just an acceleration to, say, 30 mph.

Any thoughts on this? This has been bugging me for a few years now, but the boat runs very well (except for this minor item) so I haven't been too concerned about it.

LOL, I just posted some info on this issue on another forum, so I have the answer right at hand. These clips are from Pat Ganahl's book, Street Supercharging.

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Thanks, X. That will help me with the next step if my test proves anything.

As the secondary air valve begins to open and there is strong air flow velocity at the edge of the secondary air valve edge, a small amount of fuel is drawn from an orifice in the carb body near the edge of the air valve blade. If this passage is blocked with dirt or? or not big enough, no or little fuel will be drawn in to cover the air door transition before the secondary venturii clusters have strong fuel flow.
Similar in purpose to the rear accelerator pump in a DP holley carb. Try blowing compressed air into these passages to clear them. Keep your face away from the carb when blowing out passages with compressed air.
If you want to test the carb on the primaries only, disconnect and wire the secondary throttles shut.
In marine applications some people remove the secondary air valve all together as on some boats operated in rough water the counter weighted secondary air door can start bouncing open then closed rapidly at WOT as the boats bow goes up and down over waves.
This sudden air door closing causes a over rich running condition and bogs the motor down.
Removing the air door requires that you roll into the throttle carefully to come up on plane as the secondary transition is not near as smooth. If you slam the throttle open without the air door, it will back fire.
You can experiment with the air door opening rate and timing by changing the mass of the counter weights and by changing the shape of the offset counter weight on the shaft in relation to the air valve blade position.
It would be cool if Edelbrock offered different shape and mass/weight counter weights to allow further fine tuning of the secondary air valve transitional opening on the AFB carbs.

Unfortunately the counter weighted air valve is also effected by the pitch of the boat. Does this transition only happen while the bow is high just before the hull coming up "on plane"? or also when going from part throttle but "on plane", to full throttle?

Check the fuel float level and float drop and fuel supply pressure. may need to go to the spring loaded Edelbrock "off road" needle and seats to control fuel bowl slosh effect when coming up on plane.

Excellent F-Bird. It does happen when boat is coming on plane, but the trim tabs on the boat keep bow lift to a minimum. It will NOT do it if I'm running barely on plane and stab the throttle. Hmmm.

I'll try clearing the passages, too.