88 312 Synchronizer Trouble

[312stinger.midcabin]

My 88 312 with Merc 330's has a problem with the engine synchronizer.  At idle, the needle is @ 12 o’clock as it should be.  As speed increases, the needle shifts to the right proportionately with the RPM of the engines.  I have to use my ear to synchronize them.  At WOT, it’s at 3 o’clock although my ear tells me they are running sync’d.  To put the needle on 12 o'clock, the engines will differ by ~400 rpms.  Does anyone have knowledge on how these work or how to troubleshoot them?  I’m wondering if there is a resistor or sensor that has gone bad.  Does it get its inputs simply from the tachs or from the engines?  All connections are clean and tight.  Engines are stock with OEM distributors.

You can check out my boat "Corsa Avanti" in the Registry.

BTW – CCSTINGER  --  Can’t thank you enough for maintaining this great site and the other members for their contributions here.  Ever thought about a “Stinger” poker run somewhere?

[stinger390x]

Now that's a great idea!!! Stinger poker run!

I would offer to host it at my Marina in Port Weller in Lake Ontario. We could Start and finish there. We have a wonderful restaurant there with great food and we could start off with breakfast and a start in the bay. Do a run to places all around the area and grab cards and hold the final party at the restaurant which is a cool place overlooking the bay.
We have lots of parking for trailers and the marina is fenced in as well.

Well I put my cards on the table who else is in???

Sorry to steal the thread but as for your problem the variometer situation may be a vaccume leak? Not sure which type you have but I would check for rotten and cracked hoses as they tend to dry out over the years. Look on the ontake manifold and see of any are rotted.
Secondly it might just be an adjustment on the cables themselves. See if you can syncronise the cables and the engine rpm and look at where the throttle levers are physically. There are adjustment capabilities on the cables ...
My buddy had this adjustment problem with his cables on his Stinger  last summer.
Hope that helps?

[jesse 314]

really not a super complicated system, i agree with the advice and would check hoses or eliminate it all together and just install new ones as they do get old and crack. on another topic i would love a stinger poker run but im probably one of the only ones here in the seattle, wa area with one, so i would probably come in first. but if youve never been boating here it is absolutely fantastic and really second to none, the san juan islands are incredible.

[312stinger.midcabin]

Thanks for the feedback and direction.  I am surprised to hear that it could be related to vacuum.  I expected it to be done electronically via the coil similar to a tachometer.  As soon as it’s out of storage, I’ll get on it.  I have some qualifying questions for you but I’ll hold off until I dig into it.      Many thanks!

[stinger390x]

That's why I stated I wasn't sure what type of instrument you had?
Some work electrical off the coils, and other use vaccume differentiation.

I'm not sure what unit you have.