[BIG_D]

I am having trouble with the Engine SYNC switch on the dash. When switch is activated, I slowly move the Port throttle forward (as I was told by my mechanic) and it simply increases the RPM of the motor. This just started this year! Last season the Sync switch worked flawlessly. Only difference, I put in an Electronic Control Module that connects to my Garmin Units- would that change anything within the interface?

[hiccup]

What type of synchronizer is installed? Likely a Sturdy or Glendinning. Regardless, it needs tach inputs from both engines and that probably got screwed up when you swapped stuff around for the Garmin interfacing.

[BIG_D]

What type of synchronizer is installed?  Likely a Sturdy or Glendinning.  Regardless, it needs tach inputs from both engines and that probably got screwed up when you swapped stuff around for the Garmin interfacing.

The unit is a Glendenning. I traced the problem to the switch on the dash. That has been replaced and you can audibly hear the Glendenning engage now. However, upon sea trial, the Glendenning engaged , but only the SB engine engaged with the single SB throttle advancing, but the Port (Slave) engine did not throttle up...

[hiccup]

The SB doesn't 'engage' on the Glendinning. The SB, or master, engine is directly connected to from the throttle control lever to the engine. The Glendinning has no effect on it whatsoever. The Glendinning 'interrupts' the port throttle cable between the control lever and the engine. Hearing the solenoid engage is normal when powering on the Glendinning. After hearing the solenoid engage and advancing the port throttle, do the port engine rpms increase? Does the Glendinning 'grab' the port throttle lever when at full throttle? Does it disengage properly when you power it off?

The mechanical Glendinning system uses a pair of drive cables and a differential gear mechanism to synchronize the engines. If it is engaging and disengaging correctly but not synchronizing, I would start by looking at the limit switches and then the cables themselves.

You do not need to sea trial to test the system. It can be done in neutral at the dock.

You also can reach out to Glendinning tech support. They are very helpful. Snap a few pictures next time you're at the boat.