Possible to sync carbs on 25HP 3Cyl Evinrude

[WhiteRice]

Have been having a few intermittent issues with rough idle and I know that I have adjusted the low speed idle all three carbs to about the best they can be. I have seen a few videos and have watched Dangar Marine do a few carb syncs but all of them involve using a port on the intake manifold. Well, I don't have that. Just the silencer and then the carb adapter. This motor has the "3 way linkage" so that the butterflies move in unison from the linkage on carb #2 but carb 1 and 3 appear to be slightly off from 2. I can see where to adjust the butterflies but is there a way to visually sync them other than just listening to the idle?

Also on the topic of the idle: My idle has been rough but my timing at idle is at 9 degrees. I can manually advance it to 10 and it runs much smoother but I cannot find an adjust for the idle timing. I was able to advance the timing to 20 degrees (was only at 19) at WOT with the stop adjustment but I cannot see any such part when the throttle arm is at idle. Any help with that as well would be appreciated..

 

[boobie]

What's your compression ??

 

[Faztbullet]

Only adjust in a barrel or lake as needs backpressure...cannot do on muffs and hose.

 

[WhiteRice]

Compression is 128, 129, 129

Doing this in a barrel

 

[jimmbo]

First, timing is not set/adjusted at idle, except for setting the idle speed.
The carbs need to be synced to together, and that is done with the engine off and throttle backed off. If remote controls are attached, unhook them. At that setting all the carbs must be fully closed, linkages between them adjusted so that occurs.
Sync between the carbs and spark advance will then need checking, and possibly adjusting. A factory service manual is recommended.
Max timing advance should also be checked and adjusted if needed.
Idle mixture, if adjustable, would need to be done, not fun with more than one carb. A tach, a good ear, and nearly unlimited patience needed.
Lastly, idle speed is set, by retardation of the spark timing. The actual setting will vary depending on the load the engine is experiencing, so changing to a different prop can affect it.
After idle speed is set, if there is a remote control cable, it’s length is now adjusted to provide a slight preload against the idle stop

 

[WhiteRice]

Thanks jimmbo. I came across some of that in the FSM. Having the 3 carbs is a bit of a pain with the mixture screws so I bascially seated them all and then back out 1 1/2 and started from scratch. Got the mixture pretty close on all three but only after they were all backed out almost 4 full turns. Good info on detaching the cables. Made it MUCH easier!

The idle is pretty decent right now (better than it was) but my other concern was with the idle speed. I have a pretty substantial "lunge" from neutral to forward and wanted to get the idle speed down as much as possible to help preserve the lower unit. That's just going to take some further finesse while on the water. Luckily I have a long, straight channel I can run up and down while getting some adjustments done.