Basic engine synchronization gauge question

[michaelsoption]

had same problem for years, replaced tachs with no long term success. Mechaninc replaced engine starter toggle due to an unrelated probelm and have not had a problem with the tach synch since.

My sync problems returned. When it's working it's perfect. But it's intermittant so I think it's time to break some connections, cut the wires back and reconnect. I think it's that simple.

Dan the tach problems that you are experiencing are probably something else. I experienced the same issue with both tach needles dancing around when we purchased the boat. My fix - I bought 2 new SR tachs. Sorry, I know that you didn't want to hear that, but it seems to be a common problem with the tachs themselves. I have a friend who opened one of his tachs and fixed it with lubrication, but that fix is unlikely in my opinion. Check back 6-12 months ago for another thread on tachs - I know Dominic replaced both his with digital ones and he was very happy. You might want to explore that.
Good luck!
Warren

 

[wflynn]

I just purchased a 1998 27' Sea Ray and out of the blue, I can't sync the engines within 800 rpm and the throttle positions are way different also, so it appears that the engines are running at different rpms, yet the sync needle is centered. If I use the Tacs to sync the engines, I can feel the vibration and can tell that they are out of wack. If I use the Sync guage, I end up with the engines running 800 rpms apart and they are as each throttle is apart and not close to the same position. This condition will also clear itself up and both throttles will be positioned next to each other, sync guage centered and tacs will show a 100 rpm difference or less. If the throttles themselves were not required to move so much differently, I would think it was a electronics issue, but not when a mechanical issue changes (throttles) change too. I sure could use some advise!!

 

[DaleM]

It's funny how I was just thinking to myself why are my tachs sometimes off a bunch and sometimes off only 200 or so?? I could swear that yesterday they were about 200 off. Today it seems that there was a LOT off - almost 1,000 and that concerned me. I took the lesser and synch'd off that.

Could this be one of those dirty connection issues?

 

[DaleM]

subscribed

 

[george2064]

Has anybody had a sync vibration issue, I mean the needle vibrates "goes between left to right" about 20 to 30% on either side ... it does not do it all the time ... after I have been running the engines for a while (I was coming back from a trip and when I slowed the engines it started doing that) very weird .. so I was relying on the engine rpm units after that...

 

[ZZ13]

I finally put Aetna digital tachs on my Cummins 6CTA engines. Now that I know the tach reading is spot on I took a look at the synch module and synch gauge accuracy, as I found my synch gauge needle was pushed port of center staring at about 800 rpm and got progressively worse as rpm increased (with the new gauges). Almost an entire notch on the gauge at 2200 rpm cruise. After reading up on how they work, I tested the voltages out of the module. I found the module is off, not the gauge. At same rpm it is putting out more voltage to the starboard side of the synch gauge. That's why my gauge leans left. At 1000rpm it put out 4.7v to port and 5.3v to stbd. Bigger difference at 2000 rpm. The diesel magnetic pickup versions of these modules don't seem to exist any more. Just the gas versions. I'll try playing with the zeroing screw.

 

[ZZ13]

So the centering screw did the trick. Didnt have to turn it much. Both sides put out about 5.1v now at 1000 rpm.

 

[Fly'n Family]

The best engine sync on a boat is your ears.

 

[BirdDog]

This immediately above.

Old thread, I know.

I messed with the tachs and sync gauge on our 99 310DA for a bit. In the end I unplugged the sync gauge. It is now always perfectly centered.

Tune by ear is by far the the fastest, easiest and most reliable. Twin engines spinning in tune together produce that pleasant dissonance free song of joy. Don’t have to take one’s eyes off the water nor obsess over an indication that is contrary to reality. Maybe I’m naturally inclined to trust my ear from growing up in a musically engaged family, or maybe from a couple decades flying multiengine aircraft quietly obsessing over every unusual noise...