Synchronizer & RPM gauge loss mid-cruise

[Streff]

Hello,

Engines are 375hp 3208 TA.

Cruising peacefully this morning in Alaska, synchronizer is ON.. then all of a sudden the SB engine starts revving out of control, RPM gauge goes to Zero. Port engine is all normal. I turned off the synchronizer, turned off SB engine.. Checked in the ER, all looked fine, EGT, oil pressure, engine temp, belts, etc.

It seems that the RPM data input to synchronizer from the SB engine is lost.. Synchronizer thinks it’s at Zero RPM and revs the engine. Also, The RPM data is longer feeding the dash RPM gauge. I checked the cable from the SB engine to synchronizer.. it seems plugged in fine on both sides, no obvious damage or such.

Any advise or help would be appreciated.. To start if I can get the RPM dash gauge to work, that would be very helpful to match the throttles at the helm and keep going until I dock somewhere.

Thank you

Streff

 

[tiltrider1]

What you experienced is common and fairly inexpensive to repair.

The Bad news is you can't get the Tach back without fixing the Synchronizer problem.

The most common setup is for a cable going from the front of each 3208 to the synchronizer. Coming off the back of the Synchronizer is either a cable running to each Tach or an electrical pickup and two wires running to each Tach.

Start with unscrewing the cable from the front of the 3208. You should find a shaft with an ear. If the ear is missing then you know the cable is bad. If the ear is there then pull the cable off the synchronizer and see if there is still an ear on that end. If both ends of the cable still have their ears then you probably have a short shaft and adapter still connected to the engine.

I can probably be more specific if I knew what kind of Tachs you have both helm and flybridge and what brand of synchronizer you have.

 

[Streff]

Thank you so much tiltrider,

I did unscrew the cable on both sides and found the inner metal cable is severed. It pulled out in 2 parts. I believe that this part is not a CAT part.. it’s probably a glendenning cable. I will see if I can order it to be shipped to Ketchikan.

I appreciate the assist

Streff

 

[Comodave]

I thought our Glendinning synchronizer went bad because the green light would not come on when I switched it on. Easy fix, the bulb had burned out.

 

[Streff]

Looks like Glendenning have this drive cable on back order. Will know for sure tomorrow. I am thinking of using something like a butt connector but stronger to put the 2 ends of the flex cable together for the time being. This cable turns as fast as the RPM so I am not hopeful that it will hold but it may be worth a try.

Any comments would be appreciated on how to reconnect 2 ends of a 4mm diameter flex cable that spins at 1500 rpm.

 

[tiltrider1]

Here is an alternative if the cabLe is unavailable.

https://www.aetnaengineering.com/tachometer-mechanical-senders-and-magnetic-sensors/

This gives you the option of adding an adapter that gives you both mechanical and electrical tachs. This is not a cheap option but you could at least get your tachs back. It won’t help you with the synchronizer.

 

[Streff]

Good alternative. Thank you tiltrider

 

[tiltrider1]

I use two LED Aetna tachs on my fly bridge and two mechanical tachs at my lower helm. This allows me to still sync the engines if I loose the mechanical connection.