Idle control - Big cams and carbs
 

In the mid-90's we were doing some testing with the Mercury Blackhawk drives at Lake X and Stillwater. Merc had an ignition system that over came the stalling that was common with the Bravo base Blackhawk's twin prop design going into gear from 1000-1100 RPM. The bite from the next to no-slip BH prop system generally killed the engines with stock ignitions.
Merc had a distributor w/ignition box attached that they programed for the Blackhawk's to hold the in-gear idle at about 700 RPM (they could set it at any RPM). This was an RPM based design not related to fuel or air that you see on an EFI system.
Merc flashed us set-up's that had an ignition advance to hold 700 RPM in gear, a timing ramp the same as the V-6 box and a knock sensor circuit that retarded the timing and then hunted for the highest timing without detonation. I can't remember the other features/options. These ignitions were sold with the engines.
What set-up or system is available today that would support a max of 1200 RPM in neutral and 750 RPM in gear without touching the throttle? We are still tweaking on the current carb set-up, but I don't think we are going to get there without some help from the ignition. Today, if we set the idle at 750 RPM in gear, it would be too high in neutral to go back in gear.

smaller cams and carbs...what carbs, cam, ignition timing setup and cubic inch motors are you working with?

Back4More,
The current engine set-up includes: MSD ignition @ 40 degree total timing, Holley 1150 2-circuit carbs, pump gas, single plane intake, 9.3 CR, 505 ci. 765-800+ HP (depending on exhaust) with 650+ ft lbs w/flat curve. Dart IE/Valako heads. The cam is in the 270+ X 270+ range w/.700+ net lift. The package runs great, just looking to optimize the dock manners.

With those numbers I would imagine it runs at around 6700rpm@WOT?
Is that the #7320 Dominator? Its a very big carb...a 950 is still on the big side for that ci.
More cam info please...
Which intake is it?

you need a shift interrupter.

Crane ignition has a retard function that is activated by grounding the brown wire. What if that were connected to an Alpha style interrupter?

Grounding the brown wire will pull timing at a preset level.If it is used for for shifting it then can't be used for boost retard as i use it.Great ignition.Keep the thoughts coming guys.I have a blown 540 with twin dominators and i can't get it to idle low enough to shift as i would like.Some sort of interupter would be great.

Dave Wesseldyke of WESCO Racing Engines in S.W. Michigan can build you a "shift kit" as you desire. He has built several of them for guys with Merc #6 drives when engines want to die while shift/manuvering. Dave's phone number is 616-662-2250.

KAAMA,
Thanks for the lead; I will call Dave.
Ben

There is a solenoid available that wacks the accelerator pump
when the gearshift is moved out of neutral into gear.
It is ran off the neutral safety switch.

This gives a quick shot of fuel to the carbs.

Perhaps this is the kit mentioned above.


Gerry