There is a sticky post at the top of this forum that explains link and synch on the carbs and timing tower. However, you need to familiarize yourself first with the temrs used to describe parts of the carbs linkage and timing linkage. In the pic shown, there is the horizontal swivel rod, the cam pick up, tie bar and a little bit to the left is the timing tower (where the swivel rod connects to) and at the bottom of the timing tower is the idle screw adjustment. NOTE THIS PROCEDURES IS WITH THE ASSUMPTION THE MOTOR HAS NO PROBLEM STARTING AS LONG AS THE IDLE IS SET CORRECTLY.
I recommend you do a mechanical zero'ing of the carb linkage just to make sure you correctly make the adjustment for idle. Do the following in the suggested order.
1. Remove air covers on all carbs. Place control lever in full stop position.
2. Back off the idle adjustment screw (bottom of timing tower, need to loosen lock nut) so it just barely touches (without any pressure) against the engine block
3. Check make sure the cam pick up point indicated by the hash mark or line is aligned and touching with the slot on the eccentric screw (the roller that the cam pushes against) but not pushing against. If it is not, you need to adjust the eccentric screw by loosening and turning it, so the eccentric screw slot is just touching and aligned. If the cam keeps pushing against the roller at this position, adjust the swivel so cam is just barely touching the eccentric roller.
4. Using a flashlight, look into each carb and verify the position of each throttle valve (located inside the carb at the very back end). All should be fully closed. If not adjust the tie bar as appropriate.
5. Place control lever in full WOT position. Check back the throttles position to make sure they are in full open or horizontal position with reference to the body of the carbs. If not adjust the swivel rod so the cam is all the way to its farthest travel which is at its top curve. At this point if the throttles are still not in full open position, you will need to re-adjust the tie bar.
6. Now the carb linkage is zero. You still cannot start the motor until you set your idle.
7. Set idle starting with 2~4 full turns of the idle adjustment screw (bottom of timing tower) Don't worry if idle is too high you just want to get it started at this point so you can set the idle rpm. Note, at this point the hash mark on the cam pick up should not be aligned with the slot on the eccentric screw. Instead, it should be lower than the slot marking or even lower than the roller.
8. Start the engine ( if it will not start still give the idle adj screw another full turn as required to get it started) and then set the idle rpm (using the idle adjustment screw) to about 1000~1100 on muffs neutral. The proper setting is when you are on the water and it should be around 750 RPM idle neutral.