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VDO sync issue 1997 454s

V

Verdict

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Just replaced my pickup coils in the distributors. Had my mechanic line the distributors up with the timing light. Engines run perfectly and sound excellent. I cruise around 2800 rpm’s. Both engines sound like they are in sync however my VDO sync gauge is showing port is higher.

I ran the boat on a flat calm day and with the rudders straight, the boat went perfectly straight. So to me, the rpm’s are actually in sync.

Not sure if there is an adjustment on the gauge or anything?
 

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not sure how the gauge was configured when installed but, looking at the tachs, they suggest the port is running a bit slower than the starboard.

I'd agree if the hul is going straight with the rudder centered, then the engines' rpm are close to each other but may not be in sync...I alway use my ear to listen for the beat frequency...

Assuming the sync gauge was working previously, I'd check to make sure each input wire is still providing the tach pulses from the coil. Does the sync gauge always stay fully pegged to port?

If you have the EST distributors, did the mechanic make sure they both provided full timing advance?
 
Not fully pegged. It will bounce around.

This picture is most drastic. Wish I could upload the video but size restrictions limits it.
 
you can always post the video to yuor favorite cloud storage location and then provide the link...just make sure you set the permissions to allow public access or it won't do us (readers) any good.

One trick I learned from the Mercruiser Tech Rep way back - you can assess the health of any Sync gauge by using a single source (one engine) for both inputs...if the sync gauge is functional, it should sit at zero ("in sync") regardless on the source's RPM...

And to clarify the earlier comment on the running straight assessment...the hull will run true with the rudder dead ahead when both props get the same torque (so the make the same amount of thrust)...so, if both engine make the same amount of torque at the same RPM, they will be in sync with the stated conditions...If both engines don't have the same timing curves, its highly unlikely they will provide same torque at the same rpm, especially at cruising speed.
 
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