Sync or not to Sync?

[skyscraper88]

The question I have today is about the SYNC gauge. I have noticed that when running my "twins" between 2000 - 3000 rpm, in order to keep the gauge in "sync" I must usually have the starboard side engine running quite a bit higher in order to get them in "SYNC". but when I get over 3500 rpm, they are more even in regards to the throttle position. Is there a way that I can "re-SYNC" the motors, or is it just a "feel" thing until I get on plane and up to speed? :huh:

 

[chandalen]

I also use engine sound to sync. They make a pretty hum. My throttles are never side by side even, and the rpm's are about 200 rpm off by the gauge. I too usually have a steady green sync light.

 

[RollerCoastr]

Personally, I just use my ears rather than a sync gauge. It works once you learn how to, and is more accurate than a gauge ever could be. Every once in a while, when I need my ego stoked, I flip to the synch page in Vessel View to confirm my awesomeness, and am never disappointed.

lol I have to admire your self-esteem!

Nevertheless, we've been down this road before: in a thread that discussed the fuel meters, tachs and sync gauge all claiming to be out-of-sync, but his ears were happy. As is turned out, his ears were wrong!

How many of us know that guy who beats the crap out of his engines by keeping them near WOT, or the other guy who plows along at 50% of his efficient speed because they insist "it feels right", or "sounds right"?

 

[RollerCoastr]

I'm with ya on the verification. My point is that as fallible Human Beings, our senses aren't always as hot as we think!

In the thread I referenced, the experienced boater was very reluctant to question his senses, which had betrayed him. It's not unusual.

Sometimes a slow planing speed FEELS like plowing, when in fact it may be very efficient, or vice versa! My fuel meters have taught me lessons that my gut never could.

 

[rondds]

Scraper
Read about my dilemma HERE.
I've given up trying to figure it out. I use my ears at higher RPM and the gauge at lower RPM.

 

[skyscraper88]

Scraper
Read about my dilemma HERE.
I've given up trying to figure it out. I use my ears at higher RPM and the gauge at lower RPM.

Very good info. Mine are just the opposite. They tend to be way out of sync at slower speeds and right on the money on higher ones. I am going to check the timing of both engines just for my own satisfaction.

thanks

 

[rondds]

I'd be curious if replacing my "ignition sensors" (inside the distributors) will make any difference. The grey wire from this part goes to the tach. I still have to check the timing on that port engine - keep forgetting!

 

[skyscraper88]

I am just curious on how if 2 motors running at 2500 rpm can no be in "sync" or can the rpm gauges be that far off? maybe that sensor is the key.

 

[JVM225]

I try to keep the sync gauge centered. Most of the time my tachs are right in line, but if they are ever off I would go with the sync gauge because it isn't uncommon for a tach to be wrong.
Don't go by throttle position because one cable might be a bit more stretched than the other. If there is a big difference in throttle position then you might need to take a close look at the cables.

 

[Iprof]

I am just curious on how if 2 motors running at 2500 rpm can no be in "sync" or can the rpm gauges be that far off? maybe that sensor is the key.

Before I switched my port drive to a counter rotating my engines were not the same rpm when the sync gauge was dead center. Once I switched the drive the RPM dropped on the port to less than the starboard by 200 rpm, before it was more by 200 rpm. My fuel flow does show me burning more fuel in the starboard engine but not that much more. I find my best cruising speed based on my fuel flow, I do keep the sync center and not rely on the rpm's for best cruising fuel economy. It is amazing how a few hundred rpm's can cause really bad fuel economy.

Ken

 

[aquaaddiction]

Laser tachometers are pretty cheap from ebay etc and would give you a good indication of the true rpm of each engine to compare against instruments.

Sent from my GT-I9000T using Tapatalk 2

 

[DustinL]

I keep my sync gauge a bit more to starbord. Reason is I have the OEM gauges in my boat and if I do this between the sound of the engines and the fuel flow meters it says that I am synced. At this point my throttles are off by an inch or more. If the rudder it staright and I go off the gauges my boat slightley turns to starbord everytime. According to the way I do it the RPM's match on the fuel flow. I have never operated a twin engine boat that both throttles matched when the engines were synced new or old.

 

[JVM225]

Before I switched my port drive to a counter rotating my engines were not the same rpm when the sync gauge was dead center. Once I switched the drive the RPM dropped on the port to less than the starboard by 200 rpm, before it was more by 200 rpm. My fuel flow does show me burning more fuel in the starboard engine but not that much more. I find my best cruising speed based on my fuel flow, I do keep the sync center and not rely on the rpm's for best cruising fuel economy. It is amazing how a few hundred rpm's can cause really bad fuel economy.

Ken

Just to stray off a bit:

I finally got to switch to a CR drive on the port side before launching this spring.
So far I noticed better tracking at cruising speed, and more stable turns at cruising speed. I dock alongside my bulkhead, but what little backing up I have done with the boat this year seems much improved.
Making the switch was a great move!
You gave me some info about it a while back and I wanted to thank you for it.

 

[Iprof]

Just to stray off a bit:

I finally got to switch to a CR drive on the port side before launching this spring.
So far I noticed better tracking at cruising speed, and more stable turns at cruising speed. I dock alongside my bulkhead, but what little backing up I have done with the boat this year seems much improved.
Making the switch was a great move!
You gave me some info about it a while back and I wanted to thank you for it.

Your welcome, glad I was able to help you and you are as happy as me with the CR drive.

Ken