Enigines out of sync then back in

[denders]

Hi all - looking for a place to start with this one. We have a 1982 3396 Carver Mariner with twin 350 crusader engines. As we were coming back from a day trip all of a sudden the engine sync gauge would drift to the port side ( about 3/4 of the way ) then after a second or 2 it would come back to center. You could hear a difference in the engines so it shouldn't be just a gauge issue. This would happen every 10 or 15 minutes - The Tach's did not show a difference in RPM in either engine but given the sync was only off by a little I am not surprised. We were cruising around 7 / 7.5 knots. Any thoughts would be appreciated. As an addendum - We went out again and it the issue did not reoccur until we we out about 40 minutes or so.

Thanks in advance

[Viper]

If you could hear a difference in rpm in the engines, it should have been reflected in the tach readings. Sometimes poor connections will cause this symptom or a sync gage that is on it's way out.

[feeez]

My Sync guage seems to have a mind of its own. Since I have had the boat I have always used the tachs and the sound of the engines as my sync. Out of curiosity, where is that sync guage connected to at the the engine end?

Fraser

[Viper]

They can get piggy-backed off the tachs