Sync Gauge

[inscoe]

Anyone know where the sync gauge gets its signal?

I have a 2000 290 da with T/5.0 efi's w/B2's.

The tachs read differently when the sync gauge reads "equal" and vice versa the sync gauge reads uneven with equal tach readings. The tachs show approx. 300 -500 rpm difference depending on throttle position, with an equal sync gauge. I was told by someone the gauges can be +/-10% of actual engine rpm. Is that an accurate statement?

I do not know which gauge to follow, the tachs or the sync? Is the sync tracking prop speed or engine speed?
:smt100

 

[Sundancer]

Tachs are pretty inaccurate. You can open up the back of the dashboard and there is a switch on each tach that indicates 4,6, or 8 cylinders. Move that switch back and forth a few times and then return it to the "correct" setting for your engine. The switch gets corroded and moving it a bit removes that corrosion for a while.

Use the sync gauge! It's designed for that purpose and will get you much closer to the desired setting on each engine to match the rpms. You can hear it when you get close too!

 

[inscoe]

Tachs are pretty inaccurate. You can open up the back of the dashboard and there is a switch on each tach that indicates 4,6, or 8 cylinders. Move that switch back and forth a few times and then return it to the "correct" setting for your engine. The switch gets corroded and moving it a bit removes that corrosion for a while.

Use the sync gauge! It's designed for that purpose and will get you much closer to the desired setting on each engine to match the rpms. You can hear it when you get close too!

I will have to look again, but I do not remember seeing a switch. I remember seeing a calibration pot screw adjustment. But was told not to adjust it without a computer plugged in and running WOT so true actual WOT rpm could be established. But, I have no computer and, have no idea how you can work on setting a calibration screw on the back of the tach at WOT!!!

I guess for now I will check and see if there is a switch.

 

[Sundancer]

The switches just select the cylinders. I'm not familiar with the Pot screw and I agree, I wouldn't want to be adjusting that at WOT even on a flat calm day! Maybe the newer tachs are set differently, but I don't think so. Keep us posted!

 

[Redhook98]

The sync gauge takes the same information as is sent to your tachs. It is a direct differential reading on your gauge. Your tachs on the other hand, have a much greater risk of being incorrect as they interpret the information and then have to display it correctly on the gauge. The sync just shows the difference between the two. Go with the sync and have your tachs adjusted.

 

[inscoe]

Well I will follow the sync gauge for now. I guess I must have a spent engine or something... At WOT sync gauge and tach are favoring the starboard. Stbd engine turns 5100 on the tach and port engine turns 4800 on the tach, the sync gauge is saying the port engine is underpowered also. I dont understand, the engine has not burned any oil this season. I began the season with 198hrs. and currently have 255hrs. with no oil burned... A spent engine does not make sense to me. I regularly service these engines. And previous service records show regular service intervals. Does not make sense to me.

 

[Chris Dauth]

Get hold of a hand held digital tach, run each motor up to about 2000rpm, stick the hand held on the crank shaft pulley center and adjust the dash tach to read the same.
Some digital tachs have a light pick up and you have to stick a piece of reflective tape on the pulley.
.

 

[fc3]

Except for verifying WOT, there's really no need for very accurate tachometers. Close enough, a few hundred RPM really is close enough. You don't even need tachs or a sync gauge to synchronize the engines. You can do that just by sound. When the engines are out of sync, the engine noise forms harmonics that beat against each other resulting a uneven and wavering sound. When the engine RPMs do sync up, the sound evens out and harmonizes.

You therefore can tell which is right, the sync gauges or the tachs by listening. Do a search. We discussed this before.

Best regards,
Frank

 

[Amberjack01]

My starboard tach has always been reliable, and the port tach has always been finicky. Playing with the cylinder select switch on the back has only been a temporary fix. I believe my sync gauge, and my ears, throttle levers, and fuel usage tell me I'm right.