Did quite a lot of reading on this from many sources, including Holley service manuals. All have some minor detail left out.
My first thought is this, (assuming just tuning, or just after rebuilding and reinstalling).
Warm up engine to full operating temp.
Adjust choke first; all other adjustments might be screwed up in choke is off.
Manuals, however, don't give exact distance (or conflicting info on distance choke plate should be opened while cold, as measured to the housing. Any input here? Any reference as to what level choke should be open at some given ambient temp?? Of course choke plate should be fully open once engine reaches operating temp.
Electric choke must be grounded one side, and getting 12v from source operating only when engine is running, and NOT the ignition sources, as they drop down to 9volts.
Rough-set main idle adjustment screw for 700rpm to ensure engine is at least running during test. Stop engine.
Install vacuum gauge to "full manifold vacuum". Doesn't quite show where that port is or what size hose to use, even on holley site. They show it going to automotive manifold. Any info here?
Turn both idle needles in clockwise til they stop, then back out about 1 to 1 1/2 turns...(read one turn, one and 1/4, and one and one 1/2...from various sources)
Disengage throttle cable from carb entirely. (Maybe this should be done as an earlier step...?)
With engine running, place it in forward gear, but no extra throttle.
Back out idle adjustment screws 1/8th turn at a time until vacuum goes highest it can go, turning one side 1/8, then the other, so both turned out symmetrically, until vacuum is at its highest. Here a conflict; some books say you're done; others say turn them back in 1/8th turn after you are done for "best setting".
Alternate method without vac gauge is just tune the screws (again, symmetrically, 1/8th at a time) until engine RPM is highest, assuming you can see small variations in RPM on your tach, and that it's not shaky.) Still questionable after this if you should turn those screws back in 1/8th turn after that for "best setting".
Now go back into neutral and readjust main idle adjustment stop screw (screw with spring attached) until RPM is back at 700.
Assumption now is that you replace throttle cable. If it changes RPM, then should you adjust the throttle cable itself, or the main idle adjustment screw to get back to 700 RPM?
I'm assuming at some point in time you have to manually run carb throttle thru 100 percent rotation, and then reattach cable, and run it from neutral all the way to WOT with boat throttle controls to ensure that the throttle linkages are making their whole pass from zero to WOT.
Also did more reading on adjusting the pump shot, (not included here) and a whole lot about bending arms and linkages by hand until everything is lined up...but I am assuming that if tuning a carb that hasn't heavily been messed with, this isn't really necessary??
Just emptying my mind of all the reading that I'm doing before I get my card rebuild kit in, since I think it's time for a rebuild. Got my engine running much more smootly recently, but had harder time getting up on plane pulling tube with two teens.
Still seems to run much better with no load (tube) after the small adjustments I made.
And one other thing; my carb is covered in black conformal rubber-like coating, including all of the exposed coiled springs for the throttle and by the float housing of the carb. As it comes off (little pieces are flaking off sharp-edged areas by the linkages), it gets in those springs. I don't like that. Do yours have this coating?
Update Holley Rebuild Kit Number 703-41.
Online literature not available per Holley; however, most of the pertinent info is on their newer 500CFM model 2300 carb, which you can pull PDF's up from their website to learn how to tune.
Thanks Much!!
My first thought is this, (assuming just tuning, or just after rebuilding and reinstalling).
Warm up engine to full operating temp.
Adjust choke first; all other adjustments might be screwed up in choke is off.
Manuals, however, don't give exact distance (or conflicting info on distance choke plate should be opened while cold, as measured to the housing. Any input here? Any reference as to what level choke should be open at some given ambient temp?? Of course choke plate should be fully open once engine reaches operating temp.
Electric choke must be grounded one side, and getting 12v from source operating only when engine is running, and NOT the ignition sources, as they drop down to 9volts.
Rough-set main idle adjustment screw for 700rpm to ensure engine is at least running during test. Stop engine.
Install vacuum gauge to "full manifold vacuum". Doesn't quite show where that port is or what size hose to use, even on holley site. They show it going to automotive manifold. Any info here?
Turn both idle needles in clockwise til they stop, then back out about 1 to 1 1/2 turns...(read one turn, one and 1/4, and one and one 1/2...from various sources)
Disengage throttle cable from carb entirely. (Maybe this should be done as an earlier step...?)
With engine running, place it in forward gear, but no extra throttle.
Back out idle adjustment screws 1/8th turn at a time until vacuum goes highest it can go, turning one side 1/8, then the other, so both turned out symmetrically, until vacuum is at its highest. Here a conflict; some books say you're done; others say turn them back in 1/8th turn after you are done for "best setting".
Alternate method without vac gauge is just tune the screws (again, symmetrically, 1/8th at a time) until engine RPM is highest, assuming you can see small variations in RPM on your tach, and that it's not shaky.) Still questionable after this if you should turn those screws back in 1/8th turn after that for "best setting".
Now go back into neutral and readjust main idle adjustment stop screw (screw with spring attached) until RPM is back at 700.
Assumption now is that you replace throttle cable. If it changes RPM, then should you adjust the throttle cable itself, or the main idle adjustment screw to get back to 700 RPM?
I'm assuming at some point in time you have to manually run carb throttle thru 100 percent rotation, and then reattach cable, and run it from neutral all the way to WOT with boat throttle controls to ensure that the throttle linkages are making their whole pass from zero to WOT.
Also did more reading on adjusting the pump shot, (not included here) and a whole lot about bending arms and linkages by hand until everything is lined up...but I am assuming that if tuning a carb that hasn't heavily been messed with, this isn't really necessary??
Just emptying my mind of all the reading that I'm doing before I get my card rebuild kit in, since I think it's time for a rebuild. Got my engine running much more smootly recently, but had harder time getting up on plane pulling tube with two teens.
Still seems to run much better with no load (tube) after the small adjustments I made.
And one other thing; my carb is covered in black conformal rubber-like coating, including all of the exposed coiled springs for the throttle and by the float housing of the carb. As it comes off (little pieces are flaking off sharp-edged areas by the linkages), it gets in those springs. I don't like that. Do yours have this coating?
Update Holley Rebuild Kit Number 703-41.
Online literature not available per Holley; however, most of the pertinent info is on their newer 500CFM model 2300 carb, which you can pull PDF's up from their website to learn how to tune.
Thanks Much!!
