1975 70hp surging at idle

Just got this motor. I took it out and it ran fine at WOT and then it seemed to drop a cylinder. Started back to the dock and then it seemed to drop another.Afterwards it would only start with the idle lever set all the way up and would die as soon as I tried to put it in gear. Lots of smoke and would surge.
Took boat home and pulled and cleaned out the carbs with air and acetone. They seemed fine.Pulled fuel pump apart and it looked ok with no holes in the membrane. #1 & 2 plugs seemed dark and wet. Checked ignition coils and #1 & 2 were cracked and reading open. I swapped them with the coils from my 1971 lark 50 which tested fine.
Motor starts right away but still surges on muffs.If I let it run on low dle it will eventaully die.
Motor runs fine with any 1 plug installed but starts to surge if I add any other or all 3 at low idle. Fast idle is ok with just a very rare miss but not enough to cause a surge..
Took it out again and was smoking heavily and surging at the dock. I had to jam it in gear at a higher idle so it wouldn't stall. Seemed to take off out of the hole fine and ran well all the way to wot. However it would start to surge after a short time idling in gear and then die. Bulb was hard.Applying the choke would kill it.
It would always start right up again but die when I put it in gear.
Sensor coils read 8.2, 8.3, & 8.6 ohms to black and open to ground.
Stator reads 639 ohms.
Any suggestions?
Also my SELOC manual is very vague on link and sync.
I just says the line on the cam should be in the middle of the roller upon contact. Is this the low idle position ? It does not mention what the timing should be at this position nor does it mention anything about the start line on the cam. Also, the cam is set up to pull away from the carb lever and further retard the engine. Is this correct ?
Is the low idle speed contrlled by timing alone or should the carbs be set up to open right away?
Thanks for your time .

Re: 1975 70hp surging at idle

I'm not sure about the surge, but those 3 cyls are touchy to set up, but not hard if you follow the steps correctly. The first thing that you have to do in ensure that all 3 carbs are opening at the same time. Loosen the screw that holds the roller on the middle carb, so you are sure that all 3 are not starting to open. Then attach a alligator clip with a wire attached to it to all 3 carbs at the butterfly likage. on the opposite side of the carb from the throttle linkage where the butterfly shaft comes thru the body of the carb, there is a roll pin thru the shaft. attach the alligator clip there. Then very carefully move the throttle linkage until the butterflies start to open. all 3 wires must begin to move at exactly the same time.
adjust the throttle linkages until they do. Then attach a timing light to the top cyl spark plug wire and start the motor. adjust the idle screw until you get the timeing to TDC don't worry about the RPM's just yet. Once you get the timing set to TDC, turn off the motor. Then you need to adjust the cam so the line below the start line goes thru the center of the roller on the middle carb linkage just as the cam touches it. This may involve both the roller and the cam linkage being adjusted. after you get that lined up, restart the motor, and adjust the idle screw to about 1100 RPM on muffs or 900 if you are in the water.