84 Johnson 70hp timing/sync (Groundhog Day topic)

[ElGalloFuerte]

Good morning warriors. So I’ve been cleaning up and trying to get this motor running like a champ. This is the first outboard that I’ve dug into. I’m not a stranger to motors so I feel confident attacking most any maintenance myself.

I’ve gotten to the point where I wanna learn how to sync and time this bad boy. Carbs are clean, compression is between 110-120 across the cylinders, and I have some fresh plugs and cables. I picked up a seloc manual that covers my engine, among others, and it has given me some good insight. However, when I try to fathom the timing/sync procedure, it turns to Greek. I’ve seen the recommendation to do the joe reeves procedure and I’m starting to grasp that. But not fully.

I did find a video on YouTube that shows the procedure for ‘87 and newer engines. It appears like it is identical to what the manual calls for and is much more understandable. I just wanted to get y’all’s opinion before I drink from the fire hose. I’ll put the link below.

Sorry to beat a dead horse over the timing/sync. Any knowledge would be great. Stay frosty.

https://youtu.be/uJTx-ygU23U

 

[juno pierrat]

thanks,that video will help, just got an 84" 70 and something not quit right, peg the throttle and rpm's slowly clime for 3 seconds or so then it takes off, spark advance moves to max with throttle, not sticking, only been out once, will be a work in progress

 

[classiccat]

That video gives an excellent lay-of-the-land so-to-speak. I setup my '75 70hp a few weeks back so it's still somewhat fresh in the noggin'.

1. Setting timing pointer. You'll need a piston stop tool for this...and a flexible ruler.
2. Synchronize carburetor throttle valve linkage so the throttle plates open/close at the same time.
3. Adjusting Idle Speed on the water. I wouldn't go any further until you do this. You want to be in the 750-800 RPM range when in gear and the vessel is unencumbered..make sure the cam roller is not touching the cam. Realize when you're adjusting your idle speed screw here, it's adjusting the timing base.
4. Cam Follower Pickup: this is where you attach the "throttle plate amplifier" and you want the throttle cam roller shaft to be centered with the first embossed mark on the cam just as the throttle plates twitch.
5. Adjusting throttle cam link. You might have to go back to step-4 here until you have the right relationship between the cam link, cam and cam follower so that you end-up with 0.010" gap between the cam & cam-roller when idling yet still centered on the embossed mark when the throttle plates just start opening up. (it wasn't as easy for me on my '75 as the '87 in that video :lol
6. Wide open throttle stop so that the throttle plates are open completely (roll-pins are vertical)...no further or you can damage the carbs.
7. Maximum Spark Advance. I perform the Joe Reeves method. At the ramp, I had just enough shade on the flywheel to see my white mark @ -4deg:

 

[ct1762@gmail.com]

i don't think it's the same method for the 49ci motors as the new style 56ci ones. the older ones are adjusted closer to "method B" described in the service manual for the 56ci models as the throttle cams are different, as are the linkages so Im not surprised you had a hard time doing this with an older model. the short of it is this: the throttle plates remain absolutely closed at idle. as you advance the spark lever, the timing gets bumped up gradually BEFORE additional fuel is introduced for a smooth transition. fuel before spark equals bogging and stammering and sometimes stalling completely. sounds like you got it just right classicat, but a novice might have a harder time with an older motor using the newer method.

 

[racerone]

Timing on these motor does not change for the life of the motor.----Do not make adjustments unless you are sure of what is going on.